No QB can throw a great deep ball when pressure is immediately in their face play after play. Mahomes in the Super Bowl against the Bucs was a great example of a QB with all the tools to throw deep unable to make it happen in that situation.
My 85 year old dad (at the time of that SB) hasn’t watched an NFL game in 20+ years. He tuned in to see this “Mahomes guy” he’d heard so much about - being a a guy who when stationed in the army in Baltimore likes to talk about seeing Unitas for 0.25 cents or whatever it was. As the game went on I could see him losing interest as he realized Mahomes was no more immortal than the last great QBs - who all needed protection to be great. It was such an eye opener for me as I began changing my tune around this forum. You need a really good QB, yes. You need pass pro to win a championship.