IMO the big knocks against Pace are:
* He has a very bad habit of spending (wasting IMO) draft resources to move up to grab "his guys". Drafting is a gamble by nature, and good GMs rarely trade up - you want to maximize the amount of dice rolls you get on players because some will bust out from factors outside of anyones control (injury, illness, family related issues).
* While he is good at finding undervalued FAs and mid round talents in the draft, he has a bad track record with his high picks and has a concerning amount of busts from high valued FAs who should be a known quantity. Missing on the big ticket/big money items is a not a great trait to have when thats the normal place franchises go for cornerstone players.
* He has a few concerning habits with contracts, both rewarding his own guys above likely market value and drawing out their garaunteed money into multiple years to save cap now - this is going to be subjective because we only see the contracts that players sign and rarely the ones they turn down, but the Bears have a handful of "WTF were you thinking" contracts on players that would very likely not see that amount elsewhere, and a disappointing amount of under performing players on contracts that will take 2-3 seasons to get the dead money to a point where moving on is palatable.
He definitely has his strengths though, as mentioned he is one of the best at finding under-valued players in FA and draft; he has turned the Bears into a destination for big FAs despite ownership that has a "rocky past" to put it mildly with the NFLPA and ex-players. One of what I use to think was his biggest flaw (philosophy on building OL) I am more and more starting to see as a reaction to Nagy and less as his own fault. Pace has an awful track record with identifying QBs - but outside of picking the next QB for the Bears, i'm getting more and more comfortable with him making every other decision. Looking at the GM situation from a macro level - im not sure who I have less faith in: Pace to pick next QB or McCaskeys to pick next GM.