I expected this, honestly. I watched quite a bit of those vs videos of him on youtube and you can get a good grasp of what a player is because they aren't just highlights. Jesse generally spend a more time on the ground than other DTs and doesn't do well against double teams.
Now, does this have to do with the knee? Sure, to an extent, but I had warned about this even when he was a healthy junior. He's very top heavy and has skinny legs. That combined with the fact that he often plays too high is not a good combination.
If he can learn to keep that pad level down it will help him a lot because he does have a decent burst off the LOS even with the chicken legs. He's never going to be a 1 tech/NT, IMO, but he can get to a point where he's dangerous playing the outside shoulder of the G on a 3 tech using that 1st step, good lean, and learn to use that bench press max weight to control the hands of OL. The bench press stat is nice to hear for the average fan, but in terms of football functionality is has a limited scope of use until the player can become proficient in using it in a technical manor where it becomes an amplified asset.
I think he can get to being a valuable football player though. He's not unlike our own Red Bryant, who also needed to learn to play with better leverage.