It's the line, but the reason that it's the line is the coaching.
It's amateur hour. No one is moving in synergy with everyone else. They can't run any of the running plays cleanly - you'll have guys doubling the wrong bodies, you'll have WRs screwing up and letting a DB blow up the edge, and the timing on motion is so screwed up that it's actually a detriment more than it's a utility.
I'm sorry, but installing the offense is on the coaches. We've got ENOUGH talent to run the ball. Williams is a proven competent blocker. Tomlinson is a vet who has always been average at WORST. Bradford was always sloppy in pass sets but he's a strong ass road grader. Cross is... actually pretty damn good. Barner and Brown are both plus blockers at TE. K9 is a legit talent at RB.
There is no earthly reason that this personnel should be STOPPING us from running the ball successfully. The truth is that we have an extreme void of experience on the staff, the installation of the offense has been fairly obviously botched, and there's no one there to right the ship with an experienced steady hand. Grubb and Co. are in a sink/swim scenario without an old pro to lean on.
This offense is the same one that we saw as a potential juggernaut based on 2022 and 2023. A capable offensive coach would have them looking like a fairly dangerous unit. We'll have to wait and see whether or not Grubb has what it takes, but early returns are far from reassuring.