You have to keep in mind that Clemson is far and away more talented than any team they will face this season. Not saying that doesn't mean they are not one of the best teams, simply that we cannot judge how good they truly are and won't be able to until the playoffs.
Also, we have no idea what Ohio State will be. We know what they brought back from last year's team. But they've now had to wait 2 months before starting their season, and they were under a lot more uncertainty than the SEC teams were. We know how much of a toll it took on our team, or at least have an idea. It's going to be worse for the Big Ten and Pac 12 teams. Though I suspect they'll weather it.
I know it seems like we are like Oklahoma was before this year. Awesome offense and zero defense. But there is a huge difference. It wasn't just that Oklahoma's defense was horrible... it's that their entire program has become soft. We may have technical deficiencies on defense, but we are not a soft team. Our offense is not soft. We will line up in the I formation and run the ball down your throat. Oklahoma could never do that.
We lost our 3 best defensive players to the NFL in the 1st round of the draft. We also lost our best DT, Safety and LB. So, yeah, our defense will be all new for 2020.
On offense we lost Dobbins, KJ Hill and 2 starting offensive linemen. We bring back most of our receivers and will be fine on the O-line, but RB will be something that we will have to figure out.
Honestly, the defense was the strength of our team last year and Dobbins was our offensive MVP. So, while we still have Fields, most of our team is an unknown going into the season. Tons of talent, but not a ton of experience.