I think this is the key word: "today." That was the first time, IIRC, Nagy's lost by more than 10. I could be wrong. Point I'm getting at is why I can see them firing Pace for the reasons you listed above, I don't think I'd fire Nagy yet. Even if they go 6-10 this season, he would be 18-14 after two years, and while I know that makes him a lame duck going into 2020, that's no longer a big deal and it happens quite often now. Nagy isn't a dumb guy so I'm sure he knows Trubisky stinks. The only way I can see him sticking around is if he and Pace agree to let Pace do the draft like usual except the one pick where they take a QB, it's Nagy's choice.
As for Trubisky, yes he sucks. I've done my best to remain optimistic but he's just not good and I can't see him ever being good.
The defense being overrated? I don't think so. I think Hicks is the guy who brings a nastiness and probably is the glue guy. Right now, all they have is Mack who can rush the passer. I know they beat MIN without Hicks but that may have been pure adrenaline + MIN's OL isn't very good. Floyd, as I saw someone put in another forum, is as useless as tits on a bull. Irving and Lynch are horrendous. Roquan looks like he hasn't gotten much better this year and Jackson isn't near the football as much now. So yes, perhaps a tad overrated but they had a great first 4 weeks.