It's me or the "Reactive Functional" Spring WebFlux is a stupid fad? It's hard to train new developers on it, a PITA to debug and there isn't any study which proves which it brings better performance compared to the classic Spring MVC.

It's not a stupid fad, it's a misunderstood niche. It *is* more performant for huge numbers of concurrent connections on a single node, so sometimes you have to use it out of necessity. That being said, 99% of the time people use it because it's this new, shiny thing and not because they've done the analysis that shows they need to.

That niche will pretty much disappear when loom drops in any case.