How is that different from any new codebase you have to look at? If anything Rails reduces the confusion because it has a set of agreed to conventions. I can’t think of any decently complex codebase I’ve ever come across that didn’t have it's own weird abstractions that aren’t immediately clear.

Disliking Rails’s built in abstractions seems to come down to only liking abstractions your own devs created which sounds like not invented here syndrome.