I would argue that you are fortuitously ignoring history and conference priors to your advantage. Is Bret getting heat because he had Illinois' highest pre-season ranking since 1990 and only went 8-4? No, because the fanbase has perspective of the program's past performance. That also applies to Lunney (and Henry). Again, going into a season with sky-high expectations for the program:
Lunney: best offensive season in the past 12 seasons (via SP+)
Henry: fourth best defensive season in the past 5 seasons (via SP+)
I'm choosing SP+ to my disadvantage, FEI would make these differences wider. I get that your argument is about a generational QB, which is a valid one. To counter, the offense just had their best performance since the last two program generational QBs (Scheelhaase + Kittner). That said, these are the comparisons that people will traditionally make on their opinions of coaches. Fans hold their coaches to a standard set by the program's history. Further baked into this system is the Big Ten has traditionally leaned into defense, therefore making it harder for the non-Ohio State's of the conference to have good (efficient) offenses. Facing the Wisconsin's, Iowa's, Minnesota's, Penn State's, and Michigan's defenses week-over-week makes it a lot harder to create an efficient offense compared to, say, any Big XII or ACC team.