All cache and speed optimisation plugins have one problem - compatibility with different WP themes. This one, for example, struggles with Beaver and a few themes/builders but is absolutely brilliant with Divi Theme. Wp Rocket, SWIFT, W3 Total... nothing comes even close to WP Fastest Cache on Divi. And I've tested all of them on multiple different Divi builds and server hosts.
Therefore, you shouldn't just say " plugin doesn't work" - rather, say it "doesn't work on my XYZ theme". Then it's not whining - it's learning for everyone.
Bonus tip
if you're using Divi, WPFC is great together with Autoptimize - use both for extra speed points if you need them.
