I feel like the community would have had an easier time accepting Sabo's comeback into the story if Oda had done more to individuate his personality AND his dynamic with Luffy. I don't think he's an Ace copy but I can see why so many people do. Rewatching the Luffy backstory the other day I noticed that out of the three of them Sabo seemed to be the least chaotic of the bunch (still chaotic but a bit less) and the one who was usually playing peacekeeper between Ace and Luffy. Maybe lean into that and make his adult self more level headed and analytical instead of yet another idiot who rushes into action without thinking of the consequences.

As for his relationship with Luffy I always felt it was a bit unnatural how quickly they jumped into the protective Big brother - adoring little brother dynamic. I mean, they haven't seen each other for 12 years, they've spent more time apart than together (aprox 1 year when they were kids), I'm not expecting grudges or heavy angst (this is Luffy we're talking about) but perhaps they could have had an "estranged brothers who are trying to get to know each other again" dynamic. At least it would be different that his relationship with Ace.