Also, just for comparable sake...
John is 2-4 in the playoffs post-SB, which is in the last 8 years. This includes four years of no playoffs (three consecutive) and one losing season.
Sean Payton, post-SB, is 5-7 in the playoffs, in the last 10 years. He had three straight losing seasons.
Mike Tomlin, post-SB, is 5-7 in the playoffs, in the last 12 years. While he's never had a losing season (which is why I think he belongs higher on this list), he's now gone four straight years without a playoff win, the second said stretch of his career.
Pete Carroll is 3-5 in the playoffs in the last 6 years, and has one playoff win in his last four years.
Andy Reid, who I think is actually the best coach on this list, was 1-4 in the playoffs in 5 years in KC without Mahomes as the starter. He's 6-2 since. Now he had plenty of success in Philly also, but he also had only 3 playoff wins in his last 8 years there, and 0 in his last 4.
And the guy who shouldn't be on this list, in my opinion, is Bruce Arians. He won one playoff game in 5 years as a HC in Arizona, and was not overly spectacular in TB in 2019. I give him credit for his teams never being "bad", but to me, he has all the makings of a fairly average NFL head coach that looks really good with a star QB.