I can honestly say that I did not fall into the traps that many other fans did. I continued to believe in Brown and believed he could play just fine with Tatum (although I may have traded him for Durant back when that was being rumored). I gave Mazzulla a mulligan for last season due to the circumstances but was hopeful on him and did not believe that he would be the reason for us not winning a title. And I never bought into the narrative that the owner's are cheap. Those were the most common "fan traps" and I was able to avoid them.
I did think we overpaid for White (although I liked the player). Same for Holiday. I was never critical of the trade, more neutral, I was in on Holiday from the start, just seemed like a lot to give up until both Brogdon and Williams broke down.
The final thing is one that is hard to define conclusively. I never bought into the narrative that Smart was somehow bad for the team. That he was impacting the development or the leadership of the J's. I loved getting Porzingis and 2-firsts for Smart, but I am not down on Smart. Not clear who is right on the negative Smart impact narrative. I still see it as we won the title due to the addition of Holiday and Porzingis, not due to the subtraction of Smart. That debate I guess will rage on.
It's not just the subtraction of Smart it's the massive upgrade to Jrue. Jrue fills in all the gaps and Smart kind of just did what he wanted to do. Some of that was good and some not.
Moreover Jrue doesn?t fly off the handle thinking he is knock down three point expert with heat checks. Smart just never was smart about shot selection.
I also helps that Jrue is a much better 3 point shooter than Smartacus...but I get it on the heat checks 
I have a lot of love for Smartacus, in his way he contributed to getting us to a position where we were able to win a championship, culminating in his being valued enough as a trade piece to get us KP in a three way trade.
I also feel that Smart leaving honestly opened up the door for Brown/tatum (and especially brown as we saw this playoff run) to become the leaders of this team.
I love smart, don't get me wrong and I was sad to see him traded. But at times I thought he viewed himself as the "leader" of the team. and brown/tatum deferred since he was the longest tenured player. We also saw Smart undermine mazzulla several times during last years playoff run....Jrue coming into a team already competing was more willing to play his "role" whatever that may be.
This is what I am getting at. We had Smart, Brogdon, and Williams and traded them and got back Porzingis and Holiday. You lose some talent/production (all of which ended up injured) and you bring in talent/production. That is part of any trade. It was never a trade of Smart for Holiday. Smart got us Porzingis and 2 picks, I do that trade every day.
But there is this narrative (as explained by cman88) that Smart was blocking Tatum and Brown, that he was a problem for the team. That is what is traditionally meant when you say "addition by subtraction". That you are making the team better by subtracting a locker room problem or some other problem. I never bought that in the case of Smart. Smart had his warts, but he was a core part of a team that made the finals. MEM gave up a lot to bring him in.
Keep in mind that BOS was going to trade Brogdon for Porzingis. They preferred to keep Smart. The LAC trade was plan A. They traded Marcus to get Porzingis and two firsts, it had nothing to do with Jrue Holiday (although one of the picks was part of the deal). I don't think the Celtics ever viewed Smart as a problem they had to get rid of. They had a surplus of combo guards and needed more size. Smart ended up being hurt all season so it turned out well for BOS. But I don't buy the narrative that because Smart was a certain presence in the locker room or whatever, that it was detracting from the team or from Tatum and Brown specifically.