Like I said after Game 4, they just don't have many levers they can realistically pull. Middleton can opt out of his deal and hit free agency this offseason; Milwaukee may be forced to give him a max contract or lose him for nothing and I'm not sure either of those outcomes are good for Milwaukee.
I tend to doubt Jrue will be moved as he's a pretty important part of their identity, but I suppose their identity could change depending on if they fire Budenholzer. It's even trickier because Jrue is turning 33 in a month and if you move on from him, you're probably doing it to bring back an all-star caliber PG for it to make sense...who are they going to pursue? Trae Young, pretty much the exact opposite player of Jrue? Damian Lillard, who's about to turn 33 as well? Fred VanVleet, who's a bit younger but also a significant downgrade? I think there's some semblance of a chance they could make a good enough offer for Trae or Dame if those two play hardball with their current teams, but it's probably a long shot. And I'm not sure swapping Jrue for FVV makes much sense aside from "They have to do something".
Brook is a free agent and was maybe their 2nd best player for most of the season and arguably their best player in the Miami series, but he just turned 35 and has been played off the floor in prior postseasons.
If they let Middleton or Brook walk, they'll have pretty much no cap space to replace them so those are just straight up massive downgrades.
They don't have a pick until the late 50s in this year's draft, so they won't be getting an influx of talent there either.
Bobby Portis should probably be shopped, but he's the 2nd most popular player on the team and it will look pretty terrible if they trade him after he took what was perceived to be a massive discount to come back.