Nothing wrong with how much he got paid...it was close to market value for a player in his role and experience. In comparison:
Dorance Armstrong (age 25 - 8 career sacks in 8 games started): 2 years, 12 mil
Jake Martin (age 26 - 14 career sacks in 15 games started): 3 years, 13.5 mil
Derek Barnett (age 26 - 22 career sacks in 45 games started): 3 years, 15.2 mil
Charles Harris (age 27 - 14 career sacks in 23 games started): 2 years, 13 mil
2021 Free Agents:
Samson Ekubam (age 26 - 14.5 career sacks in 24 games started): 2 years, 12 mil
Dawuane Smoot (age 26 - 11.5 career sacks in 7 games started: 2 years, 10 mil
Considering 2021 was the first season Armstrong became a regular member of the defensive rotation and had 5 sacks, it's not unusual to think he couldn't maintain production like those other players who got paid the same range but had more opportunities/starts. Plus he is one of their best special teamers