Not every community does it this way. For example, computational linguistics put most of their conference proceedings online for free: https://aclanthology.org/. Deep learning researchers just publish a lot of stuff to arxiv.
Academic publishers like Elsevier are predatory scammers.
Yep if something in CS and adjacent fields isn’t open access (or there’s a pre-print floating around somewhere) chances are it’s a textbook, not worth reading, or is obscure/arcane and was written with a typewriter. Heck some of the best stuff is blogposts by people who don’t happen to be in a publish or perish situation so why bother with journals. (Trouble with that, of course, is a lack of doi but what’s archive.org for).
Meanwhile there’s fields which can’t even figure out TeX.
