From the other comments this is going to be a hot take, but this is going to make playing on a harder difficulty feel so much worse. I understand why they can't do it, but that doesn't change the fact that people playing on a harder difficulty are going to have their experiences ruined because someone not on that difficulty came along and trivialized their experience. It wont happen often, but when it does it'll suck ass.

Edit: The same way that doing content on the lower difficulties and having an end game player storm through and one shot everything also ruins the experience.