>>58996229GameFreak recognized the importance of renewing appeal to new generations of children after the unique circumstances where Pokemon was briefly unpopular among Japanese children, spurred by their belief that Pokemon is an old fogey's franchise because of its reliance on nostalgia alone; Gen 5 was primarily causing this, since it was just "Kanto but different" in BW and then "HEY LOOK, THE OLD MONS ARE BACK!" in B2W2. New regions and characters, but the mons were just direct retreads or echoes of what Gen 1 already did, ergo, pandering to the oldheads.
This dip allowed Yo-Kai Watch to flourish for a few years, and sent GameFreak into total panic mode about how to keep the franchise evergreen with the revolving door of children, and this was an initiative they were working on prior to GO's monumental success.
Thus, Mega Evolution was made to make old Pokemon new to the current generation (special forms the old fogeys never got to use before, thus they got to say they had something they didn't), and then they followed it up with Z-Moves, Dynamax, Terastal, etc.
All gimmicks, yes, but ones that serve to make every game feel unique and belonging to the current youth with something previous generations never got to play around with before.
