Have biological theories of "evolution" 'evolved' since Charles Darwin's time or not?

Just the question iself is enough. This was also stated recently by a self-described “unbeliever”:

“to some extent it [TOE] has itself evolved”.

Really, a “theory” can “evolve” even though a “theory” is not a biological entity?!

Thankfully, the framing was welcome: “As a non believer, I do find this difficult.”

Amen to searching and trying to understand the teachings!