Not really. A lot of the mega evolutions were creatively brilliant. I'm gonna point to Mega Salamence and Mega Gengar as examples.
There were some brilliant designs for mega evolutions this gen but most of them were just atrocious or were small changes that made you wonder why they even bothered. You had megas like Mega Diancie, Mega Pidgeot, Mega Gallade and Mega Altaria, which were well designed and took what made the original Pokemon great and made it better, and then you had Mega Sharpedo, Mega Sableye, Mega Metagross, Meta Manetric, Mega Garchomp, Mega Abomisnow and yes Mega Salamence which just... weren't that good. Why bother making Salamence into a hang glider or giving Garchomp scythes for arms? That's not very creative. Neither is giving Sableye a giant gemstone to hang on to, or giving Pokemon tumors or making two Pokemon the same color. They're not the only ones; there's others out there that are either bland or have design issues and just aren't that well thought out.
Then make an arctic fox Pokémon. We have several different fox-based Pokémon. They didn't see the need to appropriate Vulpix and simply retype it to create the Zorua line or the Fennekin line.
We have two other fox Pokemon lines; the Zoroark line and the Delphox line, which isn't all that many concerning the number of foxes out there in the world. (I guess you could include the Eevee line if you wished to up it to three but I'm not entirely sure Eevee counts as a fox so I'll leave it out of formally being a fox just for simplicity's sake.) They're both very different from the Ninetales line; the Zoroark line is much more like a typical youkai than a red fox, being both an embodiment of Ninetail's traditional shapeshifting abilities and trickery and evolving into a werefox, and the Delphox line is based off the fennec fox which is farther away on the family tree compared to the red fox and artic fox. Red and artic foxes are somewhat closely related, sharing a close common ancestor, thus it would make sense for the Ninetales line to be able to essentially transition from red fox to artic fox, at least in terms of Pokemon logic.
Yeah, and you know what happens when those animal species adapt in real life to their environments to the point that it changes them significantly from their predecessors? They become a different species, not just different forms of the same one. You don't point to a Boston Terrier and say "Look, its a wolf!"
I wouldn't compare the selective breeding done by humans to domesticated animals like dogs and cats to the processes of natural selection. Dogs are bred for differing purposes, not for maximum survivability. As for species in the real world, they can and often are more closely related to each other than the ones in the Pokemon world. In the real world there are several species of similar animal that closely resemble each other and can technically even breed under special circumstances (dogs can breed with wolves, and domesticated cats can breed with wild ones, and heck tigers can breed with lions and horses can breed with donkeys and even zebras, though there are very certain limits and they won't normally breed with each other under most circumstances.) In the Pokemon world every single Pokemon is technically included in a species listed in their Pokedex entries, and they can and do jump species and even type of animal when evolving (i.e. Remoraid to Octillery, Charmeleon to Charizard, Slugma to Magcargo, and so on.) They also can breed with what should be completely different kinds of animal
living in completely separate biomes to produce offspring like Skitty and Wailord. Pokemon species in comparison to real life species just don't correlate that well at all.
Because what they've basically done here is appropriate two Pokémon that already existed and repurposed them to fill new roles that they would have been the roles filled just as well as new Pokémon. Manectric and Alakazam upon mega evolving didn't radically change––in those two examples specifically, they retained their original typing–– and even those Pokémon that did change typing at least retained part of their original typing. Here, its basically saying "We really wanted to make Ice/Fairy and Ice/Steel Pokémon but we just couldn't come up with a design, so we're repurposing some old Pokémon and making them into what would essentially be new ones."
Mega Evolution and adapting to a new environment can't really be compared like that. You're essentially comparing a superhero's transformation with Eevee evolving to keep up with its native environment; it's not a very good comparison. Mega Evolved Pokemon change through exposure to a Mega Stone and their Trainer's Key Stone, and it's a very temporary transformation while Alola Forms are Pokemon coming into a new environment and acclimating themselves to it much like Eevee did, except over a much longer period of time. Pokemon changing their appearance and types is a thing that's happened both in the trading card game and in the anime, so it only makes sense it would appear here. If you consider the Eevee line foxes we already have an artic fox in the form of Glaceon, and it mirrors what already has started to happen in Hawaii; non-native species have come in and have adapted to their new habitats.
(Sorry for the long wall of text by the way.)
