I think a more interesting discussion is what everyone's benchmarks are for a personally successful season from Mitch is?
To me, its a sliding scale of regular season stats and postseason success.
If he has another blah postseason and the Bears crash out in the playoffs but he has a great regular season, then I think in some sense we can say Trubisky had a successful season. If he posts the same regular season numbers that he had in 2018 but does better in the postseason/leads Bears to Super Bowl, then it would be really hard to say Trubisky did not personally have a successful season.
I think actual statistical benchmarks are harder to define. Trubisky's 2018 stats were weird...he made the pro bowl but was only 16th in passer rating. He didn't really kill the team with turnovers, but was only 24th in INT%. He threw deep a lot, but was only 17th in YPA. He was only 25th in Yards per game. His 'strongest metric' was TD%, where he finished 12th. Basically not close to being elite in any category.
I would say Trubisky needs to improve on his TD/INT differential...24-12 is great for a Bears QB, but average in the NFL. He either needs to complete more of these downfield passes for big plays to up his TD total to the 30's, or he needs to reduce his INT%. I think the Yards per game needs to drastically improve, although that might be dependent on how Nagy calls a game.