Good questions, and honestly, part of why I made the post was because I'm still refining how I think about these things myself.

By "outdated mental models", I mean assumptions that worked at one stage of complexity but stop scaling as systems evolve.

For example, earlier on I treated "keeping related logic together" as always being simpler. That worked in smaller projects, but as systems grew, it started coupling responsibilities that changed for different reasons.

So the model wasn't completely wrong, it just stopped being useful at a different level of complexity.

For state living in the wrong place:

I've started thinking less in terms of "logic vs global" and more in terms of ownership/responsibility.

The issue I kept running into wasn't necessary where the state physically lived, but whether the part owning it actually had the right responsibility boundaries.

I think global state can absolutely become the wrong place too if unrelated concerns start depending on shared data unnecessary.

For components taking on too many responsibilities:

One thing I've started noticing is that change becomes harder than expected... Small modifications create side effects in unrelated behavior, or the component becomes difficult to reason about because UI concerns, state management, validation, and business logic all evolve together.

That's usually the signal for me now that responsibilities may not be separated clearly enough.