>>41804709It's such a powerful mechanic that it redefines how the whole game is played, but it doesn't do it in a good way. It's a mechanic which deliberately prevents a variety of ways for your opponent to counterplay it (bypassing encore, torment, choice items, disable, destiny bond, flinching, protect and even blocking weight based moves). On top of that, it granting you boosts and beneficial weather effects on top of hitting your opponent with 101% accuracy means you build up so much momentum that it's unlikely your opponent can come back from it. There are only a very limited number of ways in the game for players to counter dynamaxed mons, which is why focus sash and ditto are seeing such prevalent usage. On top of that, predicting dynamax is significantly more difficult than z-moves and megas, as your opponent can use it at any time and on any mon.
I'm not saying that it's impossible to actually stop a dynamaxed mon, but the sheer momentum it can generate when used properly makes it extremely difficult for an opponent to come back from it.