Think about Geno in terms of that SB game we just watched vs. SF compared to Patrick Mahomes (granted tough to compare to the greatest first few seasons ever but bear with me). Geno was horrible against 3-4 defenses with disguised blitzes (SF/BAL).
Both of them have rifle arms and can make all throws.
However, Mahomes is so good at diagnosing blitzes and getting the ball out quick... running for 1st downs. Geno turns so many plays into negative plays by holding the ball or picking the wrong receiver. He's excellent in a clean pocket, and when he picks the right target, but I don't think he comes off targets very quickly and he cannot make anything happen with his legs. So, the passing stats look pretty good for Geno but I'm not sure those are perfectly indicative of a QB who tilts the field.
Could you win a SB with Geno? Maybe. If you had a coach like McVay where the progressions are easy and guys are open.. he'd be great.
When you look at big games, I feel like QBs extending plays with their legs is such an imperative quality.. Russ was never an incredible passer, but when he was so good at scrambling in the pocket, extending drives on 3rd down with his legs..etc We were soo much more difficult to beat in big games.
Patrick Mahomes JUST became the first QB ever to win a championship being paid near the top in the league.. At $50MM, you need Geno to do more than make good passes in a clean pocket. Geno does make the occasional good play where he feels the pocket and steps up, but it's not a normal occurrence.