I disagree. If you want Mixon to be relevant again they need to draft OL basically round 1-7. Dalton isn't the reason Mixon isn't getting any running room. That OL is bottom 5 in the NFL imo.
The defense having to respect the QB and the passing game goes a long way to improving the running game too. OL can be turned around rather quickly without complete overhauls, and they have invested draft capital recently in the OL. C/G Billy Price was their 1st round pick last year, and yes he's been disappointing so far but that could be due in part to lack of help around him or perhaps they just need a better scheme or OL coach. This year they drafted T/G Jonah Williams in the 1st round and then he got hurt in offseason. The Bengals absolutely need to go QB high in this draft, then they can probably draft another OL later and sign one in free agency. The Giants OL was pitiful last year, now they are decent and they just brought in one new guy, the Bengals are already guaranteed to be adding a good talent to the OL next year with Jonah coming back.