With Megas being a whole new form of a Pokémon, it's like actually removing Pokémon permanently from the game. That's pretty awful. Although I'm sure Charizard fans will have their missing Megas replaced with something new, other Pokémon certainly won't be so lucky. Mega Mawile and Lopunny were some of my favorite designs outright, so it's a big double-whammy of my favorite Pokémon not only getting their designs revoked, but their competitive viability erased, too.
For people worried about how "OP" some of them were, the only concern was in competitive. The reasonable thing to do would be to adopt rulesets that ban the Megas that are too strong (like how Smogon banished Mega Rayquaza to the Anything-Goes Realm). It's not like any Gym Leaders used Megas, so there is literally no concern for the average player regarding how broken some Megas happened to be. Competitive was the only side affected and removing them outright is just needlessly harming the casual side.
Since Z-Moves don't actually affect the Pokémon directly, it's more... understandable that they'd be gone. But it really has me set in the thought that Dynamaxing won't be seen outside of Galar, which makes me more exasperated. It's becoming harder and harder to idly sit by and just excuse Game Freak's consistent "one step forward, two steps back" design philosophy with each passing game. Instead of spending so much time and resources on a feature that is completely unnecessary and doesn't have any value in the long-term, they could have just focused more on polishing what they did have and improve elements that provide longevity to the series.
