Part of me wants to throw up my hand and just watch show casually from now on and part of me is insisting that there's still something there worth watching.
I hear you! It's difficult to suddenly switch to casual viewing, after 8 years of looking at something with an analytical mind. Looking past the surface of Supernatural has been incredibly rewarding for so long, but lately it has become incredibly frustrating, and that puts a damper even on my casual enjoyment of the show.

I just started a S8 re-watch last night
How you can stomach a S8 rewatch so soon after the season finished, I will never know. I doubt I will rewatch the season any time soon, if ever.

it just occurred to me that perhaps it's not just a matter of my brain being too full but because canon no longer adheres to its own logic (ugh, Taxi Driver)
That might very well be. You know, I really don't mind the occasional retcon or canon error. Given how complex and vast Supernatural canon is, I can't blame the writers for being forgetful of the details. However, an episode like Taxi Driver demonstrated such an utter disregard for even the most basic canon, that I have to fundamentally question the writers' competence and overall commitment to the story.