While I'm fine with the removal of Z-moves (because to me, a one time nuke was totally unnecessary), Megas are a completely different story. Pokemon that were bad and got megas to make them better (looking at Beedrill and Lopunny, Mawile too) are now back to being outright unusable again just because they want to shove a new gimmick down our throats. In fact, Dynamaxing doesn't seem that interesting to me. At least Megas has totally new designs, but with Dynamaxing, they're just making the model bigger.
On the other hand of the argument, there are some mons that didn't need megas (looking at you, Mega Rayquaza), or in the case of Mewtwo and Charizard, they didn't need two megas. It's just a shame that they continue to throw away good mechanics for one time gimmicks they're just going to add to the pile of abandoned mechanics in the next main series title.