I don't think he's still sacrificing as much now as he was a few years ago.
My first thought was wondering if he's talking about his whole career in Boston rather than right now with Tatum.
His rookie year, he's like the 8th man in the regular season, 9th man in the playoffs. Sure he had more team success, but Simmons (after sitting out a year), Ingram, Hield, Murray all got more minutes and shots as rookies. I bet most rookies in Jaylen's situation feel like they could be doing more if given the chance.
In '18, gets to start every game. And while he's 2nd in FGA during the regular season, the ball is essentially being shared evenly between with 6 guys averaging between 9.5 and 11.5 FGA. Then he steps up in the playoffs, 2nd in scoring, 1st in FGA, ups his season average by 3.5 ppg, helping the team to Game 7 of the ECF. Games of 30 and 34 in Round 1, 24 in the closeout 2 point win vs Philly in Round 2. Leading scorer in 2 games vs CLE, and 27 in another. Who wouldn't feel like they deserve a bigger role going into next year?
Then going into '19 sees a drop in minutes and shots and comes off the bench most of the year as the team tries to reincorporate Hayward, while still giving Irving, Morris, Tatum, Rozier, Smart, Horford shots.
'20 getting more shots and a bigger role, but still sharing with Hayward, and Walker replaces Irving.
Much less sacrificing since (but still probably feels like he could be All-Star in '21, and more All-NBA votes without Tatum).
Jaylen always seems like a guy who has a chip on his shoulder (has talked about high school teachers disrespecting him, Billy Donovan disrespecting him as Team USA U18 coach, fighting for the "unjust" treatment of Kyrie ), so also wouldn't be surprised for him to feel he's sacrificing something now still, but also hope he's referring more to his earlier years in Boston.