Yeah, he was average.
He was average against last year's #1 defense overall and #1 against the pass.
.....which means he played better against that Cleveland defense than 80% of the QB's that faced them last season.
Dak completed 59% of his passes against the #1 passing defense in the league last season. Joe Burrow completed 45.2%. Brock Purdy completed 44.4%.
In 17 games last season only 5 QB's didn't throw an INT against this defense last season. Both Lamar Jackson and Russell Wilson lost two fumbles against the Browns
"Average" productivity against this defense is nothing to be ashamed of. In fact, Dak should be graded higher simply for being able to protect the ball from this aggressive defense, a rare achievement last season.
The defense won this game. Next week, a different person or group of persons will be responsible for the victory. That is one of the characteristics of a contender.
There will be many games this season in which Dak will be the reason they won.