I think this is an incorrect and illogical leap.
First, I’m not sure anyone thought Middleton’s injury was the ONLY reason the Bucks didn’t make the finals. But, it was reasonable to think that the injury made their path much tougher and might have been the difference in a 7 game series with the Celtics.
This is a different year, and I think that with his multiple injuries Middleton is not as much of an impact player as he was even two years ago. Holliday is two years older too and may also be declining.
It does look like the window has closed on this collection of players being championship contenders. Even if they recover to win this series (which I don’t expect) they would have trouble with a younger, hungrier Knicks team and would be no match for the Celtics or Sixers.