You named two of what I think are part of the three outstanding QBs that never won a championship - Tarkenton and Marino. The third is Sonny Jurgenson. Fran and Dan had the teams but couldn’t get over the final hurdle. Sonny had the knowledge, arm, leadership ability, and offensive firepower - he just lacked a defense and than later in his career, had a coach who hated him. I know what if’s are for bums but just imagine what the 70’s would have been like had Lombardi not passed away from cancer.
Marino always had the arm and the smarts but he never had a Terrell Davis as Elway did when he finally won his two championships. Marino was so good I don’t think Shula and the Dolphins management thought they needed anything else. He came close - losing to a monster 49ers team in the Super Bowl (it wasn’t Marino’s fault that Montana picked apart the Dolphins D that day) and the Pats team in the AFC championship (the Pats team that then got flattened by the Bears).