Going to assume you're talking frontend? Otherwise you'd be claiming most Spring, Django, Rails, Angular, <enter common backend framework> codebases are a nightmare to work in. While there are many good application architectures that don't fit into the MVC pattern (or introduce additional layers, e.g. - auth), separating DB ops (M) from business logic (C) and endpoint handlers (V) has always been rather maintainable/testable in my experience.

Yeah, MVC (and MVVM for that matter), seem like architectural approaches that are great in theory, but with the reality of constraints, requirements, timelines, and ultimately many engineers' misunderstanding of things (frankly I'm probably included in that group as well), it just leads to a mess of interdependency and tight coupling among functionalities.

Now granted, this is pretty much a given for any architecture (nothing is perfect): so maybe my expectations of what things should be needs to be reeled in a bit.