CURIE

Many Z-moves do have a lot of strong set-up potential, though. Most notably Z-Conversion and Z-Belly Drum.

yeah Z-Conversion brought Porygon back in a big way. but remember, once you get phased or if a counter switches in, you're done, so phasers are strong against Z-porygon-Z, and Azumarill is still, despite it's bulk, at 50% hp even before the opponent's attack on that turn, leaving it vulnerable to revenge killers. it's not like mega salamence where a dangerous sweeper got better offenses, and ability-based damage boost, and the physical bulk of skarmory, and attacked all in one turn.

Agreed. Z-moves still have a place in the meta, but it's nothing game-breaking like many of the stronger Mega Evolutions.