Geth codebase query after the merge

Hello, I’m attempting to learn the way Ethereum works by going by its consumer codebase, beginning with Geth – up to now I’m very confused.

By combining the readings of ethereum.org, I now come to know geth is simply execution consumer. Then am I appropriate to say {that a} large a part of the code in Geth repository might be cleaned up? And if not, why?

Additionally: any assist or firm to review codebases collectively is far appreciated!