They are good.
Alabama will be by far the best team they have played though.
Whereas Clemson will not be by far the best team Alabama has played.
In spite of bowl losses...FSU, Notre Dame and even NC were pretty good. Louisville was decent as well, and their bowl opponent, OU, was really good, although I did think a bit over rated.
Alabama did indeed lose to a good Mississippi team. And they beat several teams similar to the NCs and FSUs...namely LSU, Miss State, Wisconsin, Tennessee, Florida, Georgia...and even TX AM. Michigan State was also really good, but matchup crushed them and Alabama played really well, making MSU look mediocre. Hell, even Arkansas and Auburn had players...and mid to lower level SEC teams are simply stronger than similar ACC teams.
Clemson can win...but this is a more major step up.