He feasts on the weak defenses, looks great, and then often times struggles to win against almost any defense that is well coached with a modicum of talent. We see him continuously make dumb, almost rookie-level mistakes, with placement of his passes, decision making, not throwing the ball away, tacking sacks, fumbles, etc. He rarely beats good defenses and pads his stats against bottom of the barrel defenses. I will say though, looking at the numbers, there are three years where even if the wins weren't produced, the numbers themselves looked really good (2016, 2017, and the parts of 2019 that he did play).
Football Outsiders, Defensive Efficiency Stat
Football Outsiders has a stat called Defensive Efficiency that ranks total defensive performance by a team over the entirety of a season. From 2011-2020 the Lions have played a total of 42 games where the opposing teams defense ended up ranked in the top 15 (at season's end). The team as a whole, and Stafford's performances have been pretty subpar over the arch of his career.
In 2011 they played defenses with a total end of season rank at 13th, 4th, 3rd, 8th, 4th.
2011 Totals: Record 2-3. Average QBR of 33.14. Average completion% of 57.48%. 10 TD, 6 INT.
In 2012 they played defenses ranked 7th, 3rd, 1st, 2nd, 2nd, 8th, 4th, 8th, 6th, 12th, 1st.
2012 Totals: Record 2-8. Average QBR of 46.02. Average completion% of 58.20%. 13 TD, 14 INT.
In 2013 they played defenses ranked 2nd, 5th, 8th, 7th, 8th, 4th, 6th.
2013 Totals: Record 1-6. Average QBR of 45.80. Average completion% of 54.98%. 12 TD, 11 INT.
In 2014 they played defenses ranked 15th, 5th, 6th, 7th.
2014 Totals: Record 0-4. Average QBR of 33.15. Average completion% of 53.38%. 2 TD, 4 INT.
In 2015 they played defenses ranked 15th, 1st, 6th, 3rd, 15th, 7th, 9th, 12th, 9th, 6th.
2015 Totals: Record 2-7. Average QBR of 45.61. Average completion% of 63.74%. 13 TD, 10 INT.
In 2016 they played defenses ranked 4th, 15th, 9th, 8th, 8th, 12th, 2nd.
2016 Totals: Record 5-2. Average QBR of 69.01. Average completion% of 67.36%. 12 TD, 2 INT.
In 2017 they played defenses ranked 3rd, 1st, 8th, 6th, 9th, 14th, 1st, 4th, 14th.
2017 Totals: Record 4-5. Average QBR of 58.91. Average completion% of 65.47%. 16 TD, 6 INT.
In 2018 they played defenses ranked 9th, 3rd, 1st, 1st, 12th, 2nd, 3rd.
2018 Totals: Record 1-6. Average QBR of 54.66. Average completion% of 68.57%. 5 TD, 4 INT.
In an injury shortened 2019 season they played defenses ranked 12th, 14th, 15th, 4th with Stafford at QB.
2019 Totals: Record 1-3. Average QBR of 70.35. Average completion% of 60.28%. 11 TD, 1 INT.
In 2020 they played one defense thus far ranked 12th.
2020 Totals: Record 0-1. Average QBR of 49.00. Average completion% of 57.1%. 1 TD, 1 INT.
Since 2011 (discounting Stafford's first two seasons lost to injury), the team and coaching staff that are as equally or more to blame for a loss as their QB Matt Stafford, are 18-45 against defenses ranked in the top 15 of Football Outsiders Defensive Efficiency metric. The team played a total of 63 games against top 15 opponents over that time period.
His average QBR, in 62 games played against top 15 ranked defenses (subtracting the Chicago game this season) is 50.74 QBR. His average completion% is 61.05%. He's thrown for 94 TD's and 58 INT's. He has a TD to INT ratio averaging approximately 1.62 TD's (per game) to .62 INT's (per game).
As I said when I posted this prior, you can chalk up his subpar play against good defenses to being the fault of someone or something else. Whether it is Linehan's/Lombardi's/Cooter's/Bevell's play calling (who I all believe have faulted Stafford and this offense on numerous occasions), the o-Line play, blocking scheme, poor receiver play, dropped passes, lack of a running game, errant penalties, injuries, blown calls by the officiating crew, lack of talent on the field, etc. I think it is fair to point out all of these problems that Stafford has faced, but his play against good to great defenses has to come under some serious scrutiny too.