This is actually a good question, and after looking up the coaches that have been inducted without winning one, it kind of goes along with my line of thinking.
You have Bud Grant, George Allen, Paul Brown, Dan Coryell, Sid Gillman, and Marv Levy.
-Gillman and Brown were around early on in the Super Bowl era, and Brown had won multiple Championships before the merger.
-Coryell and Allen are the two here I don't really get how they are in, but I'm open to listening to arguments. I get that Coryell had some lasting impact with his offensive scheme and that he had support of former coaches to get in, but doesn't seem like someone that is THAT worthy of the highest honor.
-When you get to Grant and Levy, those are the types of coaches with their careers where I think a coach in today's game could get in. They got to numerous Super Bowls, but didn't win. Not talking just one or two Super Bowls, but four or more. Levy had some damn tough competition, and you can't knock him for losing to those 90's Cowboys teams.
It does seem like most of the top coaches in today's NFL have won a Super Bowl though. You have Reid, Tomlin, McVay (not a huge fan),and Carroll.