I think we are fine at PG. Smart and Schroder are fine. There are better PGs around but I just don't see this as a weakness. If we had a good PF though, that would be improving upon Al Horford and Grant Williams. Our biggest need is a PF or more broadly, a skilled big. We start Horford and RWill and then our first "big" off the bench is GWill. That is where our biggest need is.
Offensive Efficiency - 17th
Assists per possession - 20th
Turnovers per possession - 18th
I think PG is a pretty big need
Look at the top 10 teams in offensive efficiency
Utah - Conley / Mitchell
Atlanta - Trae Young
Miami - Lowry / Butler
Phoenix - CP3
Brooklyn - Harden
Chicago - Lonzo
Charlotte - LaMelo
Milwaukee - Giannis / Holiday
Philly - Maxey / Curry
Memphis - Morant
The only odd team out here is Philly. Maxey /Curry is not a great playmaking combo. But I think that's an exception that makes the rule -- Philly has Embiid drawing attention inside. Embiid is averaging about the same number of assists as each of the guards.
Upgrading the shooting around Tatum and Brown would help, too, no doubt. But I think the Celts' current backcourt just isn't good enough.
Schroder holds the ball too long, kind does his own thing more than operate within the offense, and is not actually a very accurate passer. Smart is a decent passer, but his inability to consistently shoot makes it hard for him to really break a defense down. Not to mention that he's not really speedy enough to beat most guys off the dribble. If he's penetrating, he's usually finishing with a floater or trying to draw contact.