I used to agree with your assessment here and make the exact same argument when we had Deron. Small guys don't take teams to titles. But I think that narrative has changed a little bit. Since Isiah, Curry has been successful. Kyrie was a major part of a title. Billups was key for Detroit. Tony Parker for San Antonio. Chris Paul is currently leading the Suns pretty well. We could argue all day about Don vs those guys, but without a doubt Don is a better player than any of them through the first 4 years of their careers (CP3 vs Don would be a fun debate).
The big man thing is just a fact. Defensive minded centers with limited offensive abilities don't lead teams to titles. Just doesn't happen. We might have to go back to the days of Bill Russell to see a team win a title with a defensive center who was a top 1, 2 or 3 option on the team. All of the guys like Mutombo, Dwight, Eaton and defensive specialist limited offense guys. Now if Rudy were to take more of a Ben Wallace role, we might have a chance. Just seems that Rudy wants to be more involved and he's definitely better compensated. And Ben Wallace was an absolute unicorn freak.
We can win a title with Rudy getting paid like he is, but we need another good perimeter defender and 100% health. And maybe some 2021 Suns' style luck too.