Yeah, I agree that jQuery used to be pretty necessary for some pretty basic features in JS but is kindof obsolete now-a-days.
I don’t agree that any codebase that doesn’t use framewok X or Y will inevitably devolve into unmaintainability. If it does, it’s probably more because one isn’t following best practices. (Like the Unix Philosophy or SOLID (which functionally are kindof the same thing), DRY, ZOI, etc.) And no amount of frameworks can save you from that fate if you indeed aren’t taking steps to ensure the longer-term maintainability of your codebase.