To a large degree, I think a lot of people are behind the times. Lauri was a 4 back in the days when stretch 4's just started appearing. Nowadays, 4's are actually far more athletic and shooting the 3 is a full expectation. No one in the league wants to start a 4 who can't shoot. Pascal Siakam is a prototypical 4, not Lauri.
As another note, Lauri has never shown the ability to take advantage of smaller players. When shorter players are up on him, he struggles to shoot and can't drive by them. His size at the 4, as a result, is largely neutralized.
IMO, Lauri is a 5 in today's NBA from a size and footspeed standpoint. Unfortunately, Lauri isn't a good help defender, doesn't like to body up big players and isn't a great rebounder. He really doesn't fit here either.
I don't think Lauri has a position in today's NBA. He will have a few months to prove me and a whole bunch of other people wrong. If he can't, I would like to see him moved at the deadline. Based on a lot of what I have read here, its his end goal to go to Dallas and chill. We don't want to lose him for nothing.