Rotation is part of the game.
Rule changes are part of the game.
If people don't like those, they are free to choose a different game.
Clearly many people accept those as part of the game, and continue to strategize and innovate new decks.
Lack of medals?
I'd posit that people who are good enough at Pokémon to win medals aren't going to play a different game because they didn't get a medal as part of winning.
(If there are people who specifically left for this reason, then I'm wrong, and I'd be curious to know who they were. But then I'd say they were an exception and not an indicator of a general trend.)
The lack of communication or timeliness in delivering medals is entirely another issue, and has been suggested before, (hopefully) just a matter of thing going awry....yes perhaps more than once. But I don't believe anyone is intentionally trying to have it happen this way. I believe the people in charge, somewhere, are doing their job to the best of their ability, given constraints and things out of their power.