Not everyone plays the games for the ultra competitive aspect of the metagame, myself including, I enjoy levelling them up and beating the game, battling with my friends but that's it, there's way too many fake shiny clones out there. I'm also of the opinion that Mega's are a gimmick, which I can't stand. I also agree they change the metagame drastically but for me as a "casual fan" even though I've bought every generation, I don't like them. I'd rather they added more new pokemon, or evolved older ones instead of "mega" evolved them temporarily.
Don't you think that if they add a lot to the metagame they are more than just gimmicks?
Care to explain how? Not bashing or anything just genuinely curious
The pokémon competitive scene got real twist with Mega-evolutions.
There were Pokémon that already were competitive and gained Mega-evolutions,
like Gyrados, Lucario, Tyranitar, Garchomp, Venusaur, Alakazan, Scizor...
but there were also tons of Pokémons that were rarely or never used in competitive,
Pokémons that gained a new life and joined competitive scene thanks to their Mega-evolutions,
Charizard, Pinsir, Kangaskhan, Mawile etc
This, not only adds new Pokémons to the usual competitive metagame,
but also adds a dose of unpredictability.
Let's suppose that there was a double battle using VCG rules,
let's suppose you're facing a Charizard and a Venusaur on the first turn.
What would happen? Is Charizard going to mega-evole into a Mega-Charizard Y
and Venusaur is gonna have it speed doubled to the sunlight?
Or is it what your opponent wants you to think and then he will Mega-evolve his Charizard
to it's X form. Or would Charizard be only a bait and Venusaur is the actual one who is gonna Mega-evolve.
Now let's suppose you're gonna do a VGC single battle, then you see your opponent's pokémons.
They are: Scizor, Venusaur, Lucario, Gengar, Gyrados and Garchomp.
Do you have any idea who is gonna Mega-evolve from his team?
Probably not, since every one of them can Mega-evolve.
What happens if you see that Gyrados, are you gonna use a fighting move?
That could be super-effective if he mega-evolves,
but that would be not very effective if he doesn't
What if I told you it can get worse.
It's common in some VGC championships, especially in double battles,
that there are more than 1 poke holding a Mega-stone.
The trainer does this so he can choose for what mega-evolution would suit best for defeating his opponent.
That could make complete different strategies depending on which Pokémon Mega-evolve.
Can you see it now? I could spend a lot more time talking how drastic the Mega-evolutions are to the metagame.
But I think that wall of text summarises it well. I can keep talking about how mega-evolutions changed the metagame if you want.