They need shooting and defense and size from the guard position really badly. Financially, it makes sense that you'd shift some of the money you've put into Siakim and Anunoby into the guard position. Secondly, they overpaid Poetl for what he is. He's like a good version of a typical stiff center. He can't move well enough to guard in space and can't space the floor on offense, so was spending $20m/year on him the smartest thing?
On the optimistic side, finding guards is usually easier than finding wing/forwards like Siakim and Anunoby, so you'd think there'd be an easy trade out there for them to make.
On the negative side, the question that still remains since Leonard left is, are you just a collection of second options? Do you need to find a true no 1 to take the next step? It's hard to acquire one if you're not a popular market and don't draft the player yourself. They had to take a massive risk just to get Leonard there, and he left after one season. People are connecting them to guys like Lavine, but he's not really a no 1 and he doesn't want to go there anyway. Is Barnes a guy that eventually can convince a big star to come aboard?