If you think a QB who went 4-12 had a top 5 QB season, you are looking at the wrong stats. Somebody has to perform on bad teams simply by being on the field. Trae Young is 4th in the NBA in scoring for a team that is 34-34. He is clearly good, but would anyone say he is a top-5 NBA player this season? Hell no.
A QB's job is to win games, more than any position in pro sports. Obviously, he isn't the only person who impacts winning, but his impact on winning is substantial enough that a top-5 QB should be able to win more than 4 games on his own. Joe Burrow just dragged the fucking Bengals to the Super Bowl. Justin Herbert just pulled a sorry roster to 9-8. No top-5 QB, in the prime of his career, is going 4-12.