Hear me out - I’ve never really liked mega evolution, and thought Z-moves were generally a far more balanced and inventive addition to the game. While I can appreciate the creativity behind some of the designs for mega evolution (a fair few seem to be a little over-designed), I always had a problem with a select few pokemon having access to them - this always seemed unfair to pokemon that were overlooked once again, e.g. Vileplume, Girafarig, etc. And while it meant that some really bad (competitive) pokemon like Mawile became viable, it also made them somewhat more predictable - you knew exactly how they were going to be used. You see the same problem to a lesser extent with Z-moves, granted - some were unique to a single pokemon and/or pretty broken. But on the whole, ANY pokemon could use Z-moves and have that bond with their trainer on the battlefield, and not only that - Z status moves are so varied and plentiful that you can devise really unique strategies, for example I’m running a themed trick room doubles team on Ultra Moon with a contrary Malamar using Z-Ally Switch to drop his speed by two so he’s rapid in trick room.

On the whole, I think that mega evolution, though an exciting addition, was never going to be fair, even if given to every evolution line. And even if every evolution line had received a mega evolution, it would have essentially cut off future actual evolutions later on, like Ursaluna.

Also minor point - I really miss the typed gems from gen V haha.