DRB% I think you mean... he has a career low in TRBs% because while he tied his defensive top year, he has zero ORBs.OTOH, Smart has a career high in REB% and STL% and is shooting 1.00% from the FT line.
As you indicate, Marcus doesn't have the ball in his hand as much. Yes, he's struggling on offense. Yes if this continues it will be a huge problem. But is not an effort issue, and he should be given IMO more than 5 games particularly since he thought he would be handling the ball more but he has ended up not doing that. Plus he's always been a super streaky shooter.
From a quick look at BRef's shot chart, it looks like he's shooting corner 3Ps okay but is miserable on above-the-break 3Ps. Maybe one solution is to move him to a corner instead of above-the-break while he is waiting for someone to pass to him, although the Cs would definitely lose floor balance if that happened.
The bigger issue arises if your concerns trump my long-term optimism and Marcus continues to be abysmal on offense. Can't imagine Marcus taking benching very well, or maybe he'll get more opportunities to play with the ball in his hands.
Yeah it's 5 games, and shooting terribly is a factor, but one reason it's a factor is he's taking all his shots from 3, and he's a bad 3pt shooter. Putting him in the corner isn't the solution. He needs to either get to the rim or set up other guys... he does neither. I have no idea what he thinks his role is on the team, but it definitely is not 3pt shooter. If he were shooting poorly, but setting guys up and crashing the glass, I'd be unconcerned. But he's shooting poorly, while taking way too many of the shot he's worst at, he isn't hitting the offensive boards, he turns it over a ton while also not creating opportunities for others, there is not a single element on the offensive side of the ball he has been even decent at this year, he's been bad at every single thing.
If you built the world's worst offensive PG in a lab.... it would look a whole lot like 2021-22 Marcus Smart.