Supernatural had a return to form around season 8 and it bounced around in quality in the later seasons but never completely fell all the way off. The dynamic between Sam/Dean was always strong enough to carry the show. The final arc (Season 11-15) is a great watch honestly.
It's a super solid show with maybe 2 actual bad seasons (Seasons 7 and 9) and even Season 7 has 2 of the top 15 episodes of the series. The ending was rushed and is the main reason fans want a mini series/movie to wrap things up. But that was just the matter of Covid.
But I'll be the first to say Seasons 1-5 will always be peak Supernatural!
There's apparently rumors Jensen said in an interview he was trying to get something going with the show
The Brothers of Destruction may live again if for a short time
I'm willing to bet they get a movie deal to tie up loose ends but Jensen is pushing for a "mini series" something like 6-10 episodes. But how many times are they gonna get a "spinoff" greenlit just for it to be canceled later? lol.
Though to be fair all the other Supernatural shows were canceled because they weren't focused around Sam/Dean. This one would be.