>>45331990I'd argue that Dynamax is the worst because of how much it makes the game revolve around it.
A mega is just a really strong Pokemon that can't hold items. A Z-move is just a really strong move with 1 PP. Despite how rare and niche the situations are, there are situations where you might not want to run a Mega or a Z-move because regular mons fill the role you need better and they all would prefer to hold other items. Just like how you don't always run the mon with the biggest stats in the meta, or the move with the highest BP in the meta.
With Dynamax, it does everything and it does everything better than everything else. No matter what your strategy is, it can probably be accomplished better with Dynamax. And those 3 Dynamax turns become the only turns in the match that matter.
Megas and Z-moves are unnecessary and could be removed with nothing being lost. Dynamax actively overcentralizes the game.