This gets ugly when the state of every actor can potentially affect the state of every other actor, though. This is pretty common in games.
That's the main point the linked article is making.
My point, instead, was that FP does not break down when things get ugly; on the contrary, it gives much stronger guarantees on correctness. Of course, it takes effort to express the problem in the more restrictive functional paradigm.
This gets ugly when the state of every actor can potentially affect the state of every other actor, though. This is pretty common in games.
That's the main point the linked article is making.