Totally agree with you that now that React has matured, I have dealt with a ton of shitty React codebases because it really is more of a library that doesn't inform you how to architect your app and thus lots of folks went in completely different directions. Additionally because some of the pitfalls of React can be unintuitive, it is tough to unravel these in a larger codebase.

However, I will say it has been much easier to make updates to bad React codebases than a bad jQuery codebase. The way React works tend to make it less difficult to reason about even if the app is poorly built.