I didn't have to maintain it, actually I haven't ever worked as a programmer. But I've patched a few FOSS things abandoned around 15-25 years before that to work as a hobby activity, some kind of digital archeology.

I think people also do things now for which they'd be fired on the spot 20 years ago. Everything changes.

I suspect what you call "no standards" means in fact "different standards", but that's just a cultural difference. Some project from 1995 may use "Hungarian notation" in variable names, well, that was normal then.

That adequate version control and documentation are, eh, a bit more of a norm now, - yes.