Yes, a pass first PG can win a championship. No player can win one by himself though. Never heard of the CP3 question though but I can tell ya that it's never been CP3's fault his team didn't win. A player has to have another STAR player around them, at least to contend.
I would say few things.
1. You can win with pass first PG as the best player, but very difficult. Very rare. The problem is pass first PG like Paul isn't very gifted physically so it's hard for him to get necessary buckets or defensive stop when needed.
2. It's not exactly Paul's fault. But Wall can do things Paul can't, physically. When playoff comes, unfortunately that becomes more and more true. However, this becomes more true when you have guy like Lebron, (KD Kawhi, mostly) who can do everything Paul/Wall can do but is few inches taller and longer.
3. Wall is pass first PG, but more accurately he is great PG. He can do different things to win you the game. His one flaw is his three point shooting, but beyond that his game is off the chart.
So, i agree that he needs another star, but Paul becomes too systematic on a team. He can't give you those wow play that defines a championship teams. He can't do those plays that isn't defined.
What Wall needs is a dynamic 3/4 player who can do amazing thing on both end. Unfortunately Lebron, Kawhi, and KD are all on another team. Too bad KD didn't pick Washington, because if they had..i would have given the title to Washington.