I would not compare Smith's last season with Kuechly's really last season, the one he chose to retire on because he can no longer play like Luke Kuechly. Stats are better used when one cannot use their eyes to watch someone play.
I watched him closely in replays of the game and he is not back to the form he had at ND, he doesn't move as well or as quickly. And he was a force all over the field. If he hadn't had that injury in the bowl game, some had teams trading up to the #1 spot to get him. He played the run, covered backs and WR's and rushed the QB like a DE, he was something to watch. I am doubtful that he will ever be back to the health level he was prior to that injury and he was really dependent on his wheels and ability to change direction and accelerate at ND.
Jaylon Smith is still a very good player but he invites the criticism because it appears he celebrates individual plays when the team is out of it, seems more interested in his business than football from appearances and some still hold a grudge because they wasted a 2nd rounder that year they took him. The fact that he lost his running buddy, and the combo of Jaylon and Leighton were the best D duo in the latter half of 2018, seems lost on some critics.
Let's see how Smith, Lawrence, Vander Esch and Yosemite perform this season.