FP has also benefited from a hype cycle, and FP does improve code in a lot of ways. Making your data immutable makes it easier to reason about, and pure functions prevent surprises. However if your argument is state is bad, and FP avoids state, so that is why it is good, but you encounter a scenario in which state is required, then the benefits of FP start to degrade.

The reality is closer that, state should be immutable, and minimized as much as possible, but at the end of the day, almost every interesting problem requires storing state. Once you reach that point, classes are simply a better solution for state than closures. Especially if your class and its variables are immutable, you get all the benefits I mentioned and none of these tradeoffs. Your state is explicitly stated.