Jaylen is on the first year of a 4 year contract. Jayson starts a 4/5 year contract next season. I seriously doubt that they are going to make a trade demand in the next two to 3 years even if we continue to fall short of winning a championship. They're not stupid. And if they make such demands, we will just have to deal with it then. But people have to stop worrying about their feelings here if we are unable to compete. I don't. Man when did everyone become so sensitive to poor Jaylen and Jayson's feelings?
The nba has increasingly become about managing the feelings of your star players. If they get fed up or decide they want to team up with their friends on another team, your ability to continue to compete with those players is seriously hampered.
Just take a look at what happened in 2019 as kyrie shifted from "I'd like to be here if you'll have me" to deciding he wanted to team up with KD and Deandre in Brooklyn.
You're right that it won't matter so much in the next season or two. But once Jaylen has only a year or two left, if things have been rocky / disappointing and he's getting restless, it will quickly become a problem. I mean, we've seen guys with multiple years left on their deals (e.g. Paul George) basically force a trade.
Even setting that aside, the problem here is that if you want to be patient and wait on youth to develop around Tatum and Brown, you're only going to have a 1-2 season window to seriously compete while both of those guys are still under contract.
If we're really trying to win a championship here, and we acknowledge that we're trying to do so with a pairing of elite players who are nonetheless not in the absolute top echelon of stars in the league, it doesn't make much sense to try to pin all of our hopes on just one or two seasons. To have a decent chance of making a title run with a second tier contender, you need to be in the mix for as long as possible.
So that sets up the basic dilemma here: the Celtics need to try to be competitive in the short term, both to keep their stars contented and to not waste precious seasons with those stars under control. At the same time, they need to maintain their ability to stay competitive over the full time that they have Tatum and Brown under contract.