Vucevic seems like a very popular option among Celtics fans to target with the teams max cap space, and there have been reports that the Celtics may do just that. Allw me to briefly outline why that is a bad idea.
1) Not on our timeline, Jaylen turns 23 and Jayson 22 while Vucevic turns 29 this season.
2) Will take shots away from the Jay's when we should be trying to develop and grow their offensive abilities.
3) Plays center, a mercenary position with the highest replacement level in the league. Its a bad idea to commit big money to a center value wise.
4) He will command 3-4 years, we should be focusing on shorter term deal of no more than two years to align our self with a stack 2021 free agency. Give time for Jaylen and Jayson to become stars and make us attractive that summer.
5) He just had the best year of his career, giving big money to a guy who made one all star team and had his best year in a contract year is never a good idea. For most of his career he's been a 14-18 ppg guy.
6) If your goal is to win playoff games, a guy who just got completely shut down in the first round probably isn't the best idea. Bigger post defenders can stop him, and he will get played off the floor at the highest levels.
The Celtics best path forward should be as follows. Roll with mostly the team they currently have while adding some short term contract (two year contracts at big money, or bad money contracts for assets). See what the Jay's can do as the lead guys, whether its getting them more shots, developing their ball handling passing, running pick and rolls, ect. Go into summer 21 with Jaylen's new contract, Smart's contract, and Tatum's cap hold and rookie scale contracts as the only money on your books. Target a max level player that summer with cap space, or use the (hopefully) unprotected MEM lottery pick, young guys, and draft pick assets to trade for a star. Hell, with good timing you could do both. Notice this path doesn't work with Vucevic on a 3 or 4 year max or near max deal.
In summary, he's not a good fit, is a poor value, and doesn't fit our new timeline. Pass on Vucevic.