#2 Doesn't fit in with the young core of the Celtics
The Boston Celtics have a great young core. Jayson Tatum is one of the best young players in the league and had an awesome rookie season, leading the Celtics to the Eastern Conference finals in the absence of Kyrie Irving and Gordon Hayward.
Jaylen Brown also played an integral role during that playoff run. However, during the 2018-19 season, both Tatum and Brown struggled. They failed to fulfil their potential playing alongside Irving and the Celtics were very disappointing to watch as a unit.
For next season, they have already lost Irving and Horford and will definitely struggle to compete with the elite teams.
Kemba Walker is 29 right now. He is in his prime and his talents will be better suited to a team that's more competitive than the Celtics. Boston's young players need more time to develop into superstars and Kemba might be 33 by the time that happens.