I’m not one to put all the blame on 1 person. That’s rather naive.
Be realistic. He's been surrounded with some of the best talent in the league throughout the entirety of his career, and hasn't managed to capitalize on opportunities in the postseason. If his playoff record was average, or even below average, what you're saying would mean something. It isn't. No QB that's played in as many playoff games as Dak has a worse record. He's shown consistent failure on the biggest stages.
If you want to make the team argument, consider Dak's impact on talent acquisition. He's shown that he needs great players at WR1 and WR2 to put up positive numbers. Those cost money. He also needs a strong ground game. That means you're paying a ton to offensive linemen. Where's the money to fill holes in the defense supposed to come from?
He wants to be paid elite money, but doesn't have the skill set to compensate for less than excellent talent around him. That takes away from other positions that need to be filled. This year those are RB and DT. Maybe the old vets that were brought in can fill by committee, but the fact remains that those positions are light in the britches because money needed to be put away to sign Lamb and Dak.
If Dak were to swallow his pride and acknowledge that he needs more talent around him to succeed, sure, maybe he is the best chance in the near future. Until then, he's a very expensive problem.