Every code base that I've read that made faithful use of OOP artifacts such as inheritance (in all its forms) has been made more difficult to understand because

Every code base that I've read that made faithful use of OOP artifacts such as inheritance (in all its forms) has been made more difficult to understand because of it, rarely despite it. OOP certainly has good features (e.g. encapsulation of state), but I think it tends to shine best when programmers are really aware of the trade-offs. Most aren't. The same person that agrees that mixins are a bad idea in React, will then turn around and happily organize their logic as class-based views in Django. And due to sunk cost, it's nearly impossible to convince someone who's invested time in this paradigm that the acrobatics are often probably unnecessary. In my opinion, newer languages expose programmers to better mental models than "the class hierarchy" to solve code organizational problems. Work with Go or Elixir for a while and see your Java and Python improve.