I can go from garbage writing to relatively genius writing by comparison when my brain is fresh. I know that burnout intimately. Walk away for a bit. The story will get the respect it deserves that way. You are probably actually really close to perfect you just need the brain space to clean up that extra 5-10%. I've also thought several times that a script I wrote that I pushed myself through was garbage, came back with a fresh brain and it wasn't as bad as I thought it was during burnout.