Imperative programming isn't.
OOP is a failed metaphor, unless you use composition, not inheritance, even then, the actual basis for OOP was about the messages between objects, not the internals.
> The world is made of state and processes
No, the world is made of objects that have state and messages (events) between them.
The real problem, though, is that FP doesn’t do anything well. It’s never the fastest method of programming, which means that it needs to excel in some other way for its proponents to be right about it. Is it the most maintainable? Maybe if you have zero side effects but then any paradigm would be in that case. Once you introduce state, it becomes a nightmare to maintain, unlike OOP. It’s certainly not the most readable.
Lambda calculus, category theory, and logic are essentially 3 sides of the same coin (the Curry-Howard-Lambek correspondence). The rules of lambda calculus match those of natural deduction. It runs quite a bit deeper than you're suggesting here. It's not just some arbitrary formalism.