>>58072406
Mega evolutions are just "what if a fully evolved Pokemon could go even further by using what are essentially evolution stones made from the lifeforce of other Pokemon" and that's something that fits much pretty naturally in the world of Pokemon. It feels more akin to regional variants and way less like a gimmick than "what if you could use a supercharged move of each type by using the energy from the light Necrozma used to have" and "the dynamax/terastal phenomenon makes Pokemon transform into giants/another type from the energy of a legendary from outer space because it can."