It's easy to blame the HC when things go bad - that's why they get fired a lot. But there are a lot of things that go into making a football team good or bad.
If you step back a bit, we need a new OC, and that person surely has to be from the Belichick/Patriots coaching tree - you do not want a wholesale change in the system with a second-year QB. It's also the case that we have had terrible trouble developing WRs, and some of that has to be down to the hyper-complex scheme developed over a decade with Brady. So you want someone who is very familiar with the system but not wedded to the full complexity. So who do you suggest that should be? Bill O'Brien decided not to come here, and Patricia has way more experience than Judge, who was basically a Special Teams coach.
Patricia is super-smart, but his attempts to impose "the Patriots Way" on the Lions did not go well (sounds familiar - McDaniels his first time as head coach also went similarly badly).
This is a good description of what went wrong
(link doesn't want to post for some reason so copy and remove the space)
WHEN THE PATRIOT WAY GOES WRONG
https: //bleacherreport.com/articles/2917777