>>58639724I maxed out my shiny Mawile’s mega level and I mega evolve it any time there’s an event for fairy or steel spawns that I want to reap the extra candy from. So while useless for anything else, I do get a lot of mileage out of it.
I’m an autist so I figured out which megas I had to max out to have the fewest number of pokemon but still cover all the types… i have it down to 8 pokemon covering all 18 types and Mawile is one of those 8. But no real other reason you couldn’t max out those others you mentioned and get some use out of them