2. Trenton Simpson saw his stats decline from year to year
The case for keeping Trenton Simpson as a big slot would be that his 2021 season was better than his 2022 season. How about this, he rushed the passer 90 times in 2021 and totaled 31 pressures. He rushed the passer 109 times last season and had just 16 pressures. It is easier to blitz off the edge without a blocker in front of you, and he is more of a straight-line athlete than a block deconstructor.
More than that, his run defense got worse as well. He went from a 10% run-stop rate in 2021 to a 6.6% run-stop rate last season. Again, this is probably because it is easier to stop the run, but still, it does show that Simpson struggled when asked to do more traditional linebacker things.
Lastly, while you think he would be better off in coverage because the one bigger challenge in the slot is coverage, he also saw his coverage skills decline. It was a bit more minimal, from 0.62 yards per snap in coverage to 0.69. Still, his yards after the catch also jumped from 7.5 to 8.5. This showed as Simpson could win in man as a better athlete, but when he had to pass off routes and make plays over the middle of the field, he was a bit more undisciplined.
There can be two arguments here. First, he is a big slot, and after losing Kyle Hamilton the team could use a big slot. The second is that he is still best off as a linebacker, but a year behind Patrick Queen could be what he needs before he is ready to see the NFL field.