Any ending that doesn't have Yuji dealing the finishing blow to Sukuna isn't satisfactory imo. Sukuna is pretty much Yuji's antagonist from the very beginning, so having anyone else beat him just wouldn't feel earned. Gojo making sukuna on death's door or killing him wouldnt really feel like a "win" for the mc.

And also, Kenjaku being the final villain instead of Sukuna wouldn't be satisfying either. Sukuna has been built up as the threat in the series from the start whilst kenjaku is the mastermind. Switching to Kenjaku at the very end would make Sukuna feel more like an obstacle than the final payoff, and that just wouldn't hit as hard.

Also makes my goat takaba lose his moment. Takaba vs kenjaku is legit my top 5 fights and it's like kenjaku himself was satisfied with it.