The problem with MIL is that you have Giannis and Middleton... but that's it.
That's how we beat them last year (even w/o Kyrie + Hayward), we just had better depth and credit to some of our guys for playing great defense (especially Ojeyele. Idk what else he could have done against the Freak but especially in the home games I thought he did pretty well given the circumstances).
Now of course if they can add another star FA next summer (along with keeping Middleton), then that's a true Finals threat. Like I said before, I was a bit shocked they didn't do something like Middleton + Picks + Salary to acquire Leonard and try a Leonard+Giannis pairing (unstoppable!). Like most have said here, it's hard to imagine many FA's just deciding to go to MIL, so they may have to make a move or two to make it happen (a trade).