As far as rebounding goes..
JI is a good rebounder, but not if he's going up against a very good rebounding center. Keep in mind JI doesnt play a lot center minutes. According to BBallref he played 13% of his minutes at SF. 87% at PF. He definitely played some center minutes, so bballref not accurate, but that was rare and against certain lineups. All of a sudden, he finds himself the starting center in the play offs against a big front court with good rebounders. There is a reason for that, and its the same reason Isaac started last game of the regular season. WCJ's back is still hurt. I could see when he checked out he walked to the bench very slowly and looked in pain when he sat down.
If they want to win the rebounding battle, the Magic can play a Paolo-Isaac-WCJ front court. We have seen that a few times throughout the regular season. We saw it to close out the win against the Wolves and their big front court. It worked very well. If WCJ was healthy we definitely wouldve seen it today IMO.
As far as the guards.. yeah its obvious they need another guard. Anyone who watched the Magic regularly knew that was the case. Magic fans knew that. Thats why you always see someone suggesting a trade for a guard on the trades and transactions board everyday

. Suggs had a bad shooting game. **** happens, he still shot 40% in the regular season. The 3s looked good. Harris is a proven vet shooter, not a volume shooter but he doesnt usually miss open threes like he did today. Both played good defense. Cole is and always been inconsistent. Could give you 25 next game and i woudnt be surprised lol. Unfortunately, we were all hoping Cole was going to build on his improvement last season, instead his 3pt% has regressed to below 34%. Fultz TOS came back and at one point his shot looked like it did during his rookie season.
Clearly they need to upgrade atleast one of Cole/Harris and get rid of Fultz (who will be replaced by Black). They have the means to do that with cap space and assets. The FO messed up this offseason. They didnt think Fultz and Cole would regress and didnt think this team would be a 47 win team. Then they also messed up again before the trade deadline when they saw they can compete and need a guard upgrade and didnt do anything. They will have to do something this offseason. Maybe this play off series will finally convince them.