Before I address that, I notice that you asked what would be God's purpose for creating so many things so that they are not exactly and simply as they easily may appear. Well, I see at least two issues there, and one of which you already mentioned: we are fallen. And I, as a YEC, take this to include biologically and neurocognitively. Combined with culturally, that means we all are in serious need of a certain kind of education. I've barely just begun mine as a human being, and I'm 50 (and I began it at 5 (five), and began it at full force at 25).
The second issue seems the most palpably obvious to me. The more complex and nuanced is the natural world, including physics, biology, etc., the more, and deeper, and broader are its potential technical applications. Imagine if all these realms were only what they seem to be to some dogmatically 'practical' tribe whose level of science and tech is at the Stone Age? Compound this with such a tribe as has been bio-culturally devolved to be very dull-witted to the basics of the natural world, and of procedural thought, and we can forget about nearly everything that, today, we take as the basic-level sense about tech-science.
Now, about what I quoted of you.
The same principle applies for being posed to us YEC's concerning OEC's and TE's. But so far I have not found many (if any) of my fellow YEC's who will actually put the human beings who are OEC and TE in the same conceptual prime box as these YEC's ought (and fortunately often do) put themselves.
Even atheists are human beings, and thus who as much bear God's essential image as any Christian. So even atheists can, and often do, have (not strictly originate) ideas that, while right, or at least partly right, are ideas that many YEC's (and, I would guess, some OEC's and TE's) reject because of the 'messenger', so to speak.
On a personal note, I am here right now because of at least one atheist, who I could name, but won't. It was largely (but not initially nor mainly) due to him that I am a 'rogue' version of YEC. He, for reasons that I think he would like to ascribe mainly to his atheism, taught certain things that compounded the reasons why am both very much YEC and 'rogue' YEC.
I do not fall in line with certain status quo tenets of most YEC's. This is precisely because I see these certain tenets as actually, and most profoundly, contrary to Biblically-based YEC (one can image a non-Bible founded YEC). Hence I might be considered by most YEC's to have 'departed, slightly, from the proper fold."
Here is a sample of what I have to say to my fellow YEC's that seemingly nearly all of them would call 'beyond the true fold':
Every human that ever lived has most naturally wanted to know how the universe and Earth came to be. That is, there is nothing natural, nor right, about avoiding the question, or about having no deep interest in it. And every natural culture centrally wants to know how that Earth works: how it supports life. By no Divine caprice, we human kind were created on a completed living planet, and this in the daytime. This is why the universally normal approach to Genesis chapter 1 sees that it emphasizes Earth as a proper member of the cosmos, as opposed to being alien to it. The analogy to man and woman is thus at least effectively maintained.
So, unless God is shallow or largely arbitrary, all of this implies every profound practical and empirical Providence which a living home in the cosmos can provide. For, though God logically has the power to, He clearly is not of such character as to have created us inside a nearly-windowless, non-rotating space ship in intergalactic space. God is the God of the living and the natural, not of the non-living and the artificial. This is why, when God first appeared to Moses (from within the unaccountably burning bush), He told him not to approach until he had removed his footwear from off his feet (Exodus 3: 3-5).
This all suggests that the order in which the Bible's first two subjects is presented is that of the narrative analogue to an arrow: 'heavens' and 'Earth'. It also explains why everyone most naturally takes this pair to be (a) the general realm over their heads and (b) the general life-filled realm around them. But more to the point, everyone senses, if only subconsciously, that this order is that of the general context immediately followed by its special subject. In fact, this sense is confirmed by the sole subject of v. 2, and re-confirmed all the way to the climax in Genesis 2:23. And the particular things that Genesis 1:2 says lets every reader know that what they are about to read is not only a cosmology, but one that promises to glorify the Living God in every narrative way possible.
Unfortunately, the universally normal approach to Genesis 1 has often been confused with a passively 'plain' approach. The passive approach expects the account to spell out, in the most specific way, every part of the account that its author knows to be crucial to a complete basic understanding of the whole. Clearly this does not work for Genesis 2, as most every skeptic thereof demonstrates. This passively loyal/selfish way of 'interpreting' a given text may be amenable to the rote memorization of that text. But no humble author of a real and profound account would rather that his disciples more assent, dogmatically, to his verbatim than to know or to seek his meaning. For, to assent by way of a selfishly passive frame of mind is to risk assenting to (or else ridiculing as interpretively correct) a false impression of some bits of that author's verbatim. Such can only lead to a loyalty to something that the author would never want his readers to ascribe to himself.
So, in contrast to a passive hermeneutic of Genesis 1 is the natural, life-centric one. The natural one finds that the account is universally accessible and relevant. This is core of 'YEC'. The problem is the psychological force of what the loyally/selfishly passive approach finds. That approach is the most natural to itself, especially in face of certain seeming oddities in the account. Hence the passive hermeneutic becomes only more passive, more narrow, more simplistic, and thus either more trepidly loyal to its resulting notion of Biblical Theology, or more deeply confirmed in its ridicule of theology-and-Bible as such.
Perhaps one of the first-published espousals of the trepidly loyalistic version of the theology of Genesis 1 is that of Theophilus in the first Century A.D.. Theophilus, likely motivated partly by a selfish kind of polemic interest, uncritically interpreted Genesis 1:1, 3 and 14-18 to say that the Sun, Moon, and stars were created days hence of the creation of both Earth and light (Genesis 1:3-19). And, at least with Theophilus himself, if not with persons in earlier centuries, this Days Prior (DsP) interpretation of that light has most commonly been understood to be a genuine oddity; a truly arbitrary order.
This arbitrariness is why Theophilus rationalized it as that of God's taking a foreknowing preemptive action against the fact that some fallen people would use the natural hierarchy to reject God's Creator-hood. Specifically: (1) those who favor a godless cosmology appeal ultimately to the perceivable general hierarchy-of-dependence between life and non-life, and (2) God therefore reacted preemptively by creating the two main things thereof in reverse order: Earth and plant life prior to the Sun; and, thus, light itself prior to the Sun.
Recently, in the interest of fully providential, as well as modern polemic, relevance, those such as DeRemer et al (see link below) reason that this seemingly arbitrary order between light and Sun actually is meant to be that of the physics of light. According to modern knowledge of the physics of light, it indeed would be the most natural for God to create light prior to creating any stable luminaries. On this view of the explicit terms of Genesis 1, the 'light' of v. 3 is not merely the visible light by which humans see the world, but is the total spectrum of energies that emanate from 'atomically structured' matter. This is a compelling finding from Genesis 1:1-3, especially since even plant life is known today to rely on more than just the narrow sub-spectra that are visible to humans. Nevertheless, within the entire account, that is what v. 3 best implies anyway, not some narrowly anthropocentric reading of the Hebrew.
And, within the universally normal reading of Genesis 1, the Days-Prior (DsP) interpretation of 'light' easily is unnecessary to a physically correct bio-floration of light. Moreover, the textual possibility for the full naturalization of this DsP interpretation need be thought of as nothing more than the inherent cognates of the universally normative subjects and their order of presentation. Specifically, that the language, subjects, and sequences of the first eight verses may actually be meant to allow a secondary-level, physics-focused, v. 1-appropriate, account within the same text. In fact, it is only by our allowing the universally normal reading that we can find that the account properly addresses every physical realm of human concern: the prime, or main level of meaning being that to life and life-support; and the secondary level being to a universal physics that resides in v. 1. The connection between the two levels, especially by the life-favoring fine-tuning of the cosmological constants, would then reflect the man-woman relation in every way.
DeRemer, F., M. Amunrud, and D. Dobberpuhl. 2007. Days 1-4. Journal of Creation 21, no.3:69-76, https://creation.com/images/pdfs/tj/j21_3/j21_3_69-76.pdf.