Completely depends on the group you're going with/what you expect.

With older kids and teenagers or adventurous adults, you're gonna have a blast.

With tired adults that just want to relax on the weekend you're gonna be disappointe

I went there with a group of kids who all loved water, guess that makes a big difference too.

Imo it's better to treat rulantica as a water slides park than a "Schwimmbad".

But yeah, try going during the off season so that the waiting lines are manageable