Both things can be true. The coaching can be not good along with NIL not being good either. It's equally lazy to just excuse everything else because of NIL.
When it comes to Diebler so far, he's a coach with no figured-out identity of his own and it really shows with the team. The offense is usually just a mess of 5 guys trying to play 1 on 1 ball. which really only works if you have a absolutely loaded roster. Defensively the individual talent is not good but there is just no direction and cohesion as a unit, you can make up some for individual faults if you have a good plan in place, but we do not have that, the result is guys looking like they are lost a lot of the time and giving up the comical amount of wide open looks that we do. These are things that good coaches can somewhat mend with a good system and plan, now no coach is taking this team to the sweet 16 or beyond, but I don't think you let bad coaching off the hook just because Diebler doesn't have a highly funded roster. YES, NIL needs to get better. But the actual coaching by Diebler needs to wildly improve next season as well.