I'm going to frame my assessment based on not only what we have right now, but what I anticipate we'll need in the near future after free agency this off-season. The short answer is I think we need the rim protection and rebounding normally provided from the starting center spot in this era of positionless basketball. Such a player would hopefully come in the form of a long, athletic and energetic big man.
Gortat is up there in age and likely gone after this season. Harrell is undersized in terms of length and it remains to be seen if he can maintain his all-out play in extended minutes over the course of a full season. Marjanovic may return on an inexpensive deal but he's still more of a spot contributor than regular role player in the rotation.
The way I see it, we'll also need more shooters as Gallinari will likely not be with the team after next season, if not sooner. I anticipate that we'll sign Kawhi this off-season, so I have the Clippers' composition with him in mind. I think the team can make do with just Kawhi and re-signing Tobias this summer, but down the line we'll likely need that proverbial second star player to seriously contend.
If Durant were to be that player, this would actually fill most of the void for shooters but we'd still have that need for the aforementioned big man, which is probably why the
current consensus board opinion has either the Brow or Greek Freak as the preferred partner for Kawhi. I've also mentioned elsewhere how signing Khris Middleton along with retaining Tobias to complement adding Kawhi might be a more appealing option over Durant while we wait for the situations with Davis and Antetokounmpo to develop.
Another area of need could be argued for a more natural playmaking point guard but I think Shai is a suitable player even if he is more of a facilitator than playmaker. Shai's length and versatility would provide many options on both the defensive and offensive ends of the court as he continues to develop. He's already off to a great start and his lack of natural playmaking ability is mitigated by incoming ball-dominant free agent(s).
Jerome's development would also serve us well as he's already got the ability to contribute as a shooter, but whether that will be as a starter or designated shooter remains to be determined as he works on building his confidence and defensive ability. I'd also love to have an athletic starting shooting guard but the priority and biggest need remains a reliably consistent starting center for the foreseeable future.