In his first year, Prescott threw for 13 touchdowns and 4 interceptions against above-.500 teams and compiled a 6-3 record, including the playoffs. Since then, his touchdown-to-interception ratio is 25-25 and his record as a starter is 6-17. Last year, he had an 8/8 TD/INT ratio and the Cowboys went 1-6 against teams with an above-.500 record.
Of course, you may be asking yourself, well, how do other top-paid QBs fair against quality competition? How do Prescott's stats stack up against those in the pay range he's looking to break into? I'm happy you asked.
Against over-.500 teams both in the regular season and the playoffs (when applicable),
Aaron Rodgers had a 12/4 ratio and 5-3 record last year. Russell Wilson had an 11/4 ratio and a 4-4 record.
Kirk Cousins had a 15/6 ratio and a 3-5 record.
Jared Goff's ratio was 6/6 and his record was 2-4.
Tom Brady was 6/5 and 3-4.
Patrick Mahomes, Lamar Jackson, and Deshaun Watson, Prescott's QB contemporaries also up for new deals soon, had numbers of 20/4 and 5-2, 10/3 and 5-2 and 12/5 and 4-3, respectively.
While Prescott isn't alone in his struggles against better teams, all of those quarterbacks outside of Goff were better than Prescott against elite competition last year. For the quarterbacks around his same age and stature (yes, Mahomes and Jackson are MVPs, but you get it), Prescott isn't even in the same ballpark.
What's interesting here is I'm pretty sure a deeper analysis will show Dak's head coach had the same issues against winning teams/QBs.
https://www.thebiglead.com/posts/cowboys-dak-prescott-stats-good-teams-contract-01e8w476239v