Overall grade on this mock trade
I do really like the addition of Brown for the Bucks, and he is the ideal trade target. He is also the ideal trade target for a lot of contenders and teams to put themselves into contention. He is someone who can hit the deep shots consistently but ultimately play defense is what is valuable in the postseason, similar to P.J. Tucker in 2021 and how he elevated the Bucks on both sides of the ball.
It is what Milwaukee gives up that is a slight concern. Giving up two of your most played bench players in return for just one could be more of a detriment to the rotation than the positive of what Brown can bring to the roster. It could potentially make the front office activate the club option on Brown's contract and that would then restrict the moves the Bucks could make in the offseason.
The Raptors would get two veteran players that they could then look to move on or keep as they are under contract. Their asking price may also be higher than what the Bucks can offer, so that may be what turns them away from making this deal.
A defensive lineup with Brook Lopez, Giannis, Crowder, Brown and Lillard would answer the defensive problems, and you would still have scorers in Middleton and Beasley to use. I do, however, think it would leave the frontcourt very light with just Giannis and Lopez there.
It is a difficult trade to grade, but it would also get the Bucks what they need, and sometimes, that can take a lot.