Some people said that about Vogt too, but he got beat up in the American.
I've watched about 45 mins of Ivanauskas now, probably about all I will watch for a while. He seems to just quit on plays now and then and even in 2018-19 was outmatched defending at the 4. Even when he guarded his guy well, he didn't provide help defense, because he knew he couldn't recover.
I think he could be good enough defensively, but probably playing the 5. He has the height and frame to put on 10-15 more lbs. At the 4 he's going to have to defend a lot of smaller and more athletic guys. At the 5 if he puts on some weight he's not going to face many guys too big for him to defend (and we have Vogt if that does happen).
He does have a nice handle on offense, is a good passer and has a nice finishing touch. If Diarra can continue to knock down threes, Ivanauskas will be hard to stop surrounded by shooters.