At least in VGC I'd say Z-moves would be kinda dumb in a Best of 1 format since you can easily be cheesed out by something dumb because of a random Z-move you couldn't have possibly expected. With Best of 3 I'm more okay with the idea of Z-moves since it becomes more strategic with how you use your Z-move, and you can't take wins with surprise gimmick Z-moves as easily.
They're like Gems to the extreme and I know in past VGC formats people have had very lukewarm opinions of Gems (hi Dragon Gem Latios), so I'm honestly hesitant to say VGC this year will be a "better" format than last year, but it's definitely fun right now knowing that Best of 3 will still be a thing. As a whole I'm still a bigger fan of Mega Evolutions though. In other formats I feel like the utility of a Mega is more necessary than Z-moves, I don't even feel like I always need a Z-move on a team and sometimes wonder if another item may be just better.
They're like Gems to the extreme and I know in past VGC formats people have had very lukewarm opinions of Gems (hi Dragon Gem Latios), so I'm honestly hesitant to say VGC this year will be a "better" format than last year, but it's definitely fun right now knowing that Best of 3 will still be a thing. As a whole I'm still a bigger fan of Mega Evolutions though. In other formats I feel like the utility of a Mega is more necessary than Z-moves, I don't even feel like I always need a Z-move on a team and sometimes wonder if another item may be just better.