I'm playing 8 gachas right now, definitely doable if you manage well and treat a few of them casually without letting FOMO get to you but I feel like I reached my absolute limit, if I want to pick up a new one I'd have to either drop one of them or abandon the thought of playing "normal" games for a while. That said I know people who play like a dozen of them.
As for whether it's worth it or not, it's your time and your money, only you get to decide.