That's certainly a possibility. Another possibility is that the hatred just rubbed off on Chuck and not God. Chuck was twisted and was somehow able to wrest control of God's powers for himself.

Or perhaps in the beginning God and the Darkness were separate, but in the Season 11 finale when we see them flying off and swirling together, perhaps they mixed into what was almost a single being for the first time before deciding they had had enough and separated before Season 14, and that mixing allowed them to affect each other in a way they weren't able to in the beginning when they were separate. Under this line of thought, perhaps they were able to mix and separate because both agreed on the mixing and separating willingly. But when they merged in Season 15, Chuck wasn't willing to let Amara separate from him again.

For me Season 8 was a big improvement over 6 and 7. 10 was a big improvement over 9 (but that's because 9 was terrible). 11 was an improvement over 10. 12 was a sizeable improvement over 11 (though that's because I'm a canon nerd, and 12's continuity was the best the series ever got after Season 5, filling in plot holes and unresolved storylines from Seasons 5-9 and recontextualizing the events of Season 6 in a way that slightly improved that season; the actual story of 12 was a step down from 11 if you shut your brain off for both seasons, but 12 did actually make sense in a way 11 didn't). After that it was basically downhill except that 15 was just slightly better than 14 for me.

Basically the show still has plenty of ups and downs after Season 5, and I think I still agree with the "net positive" thing because most of the later episodes of Supernatural are still entertaining even if they're not up to the standard of the first five seasons. The number of outright bad episodes is less than the number of good or neutral episodes by a long shot.

As far as I'm concerned, it basically is. Season 11 told us that Chuck was God's meatsuit, that Chuck had his own personality that God was adopting too much as his own, and there's just so many things that don't make sense if Chuck is God in human form rather than a human vessel for God. And since Amara starts acting good and appreciating creation after spending time with God, in my head it makes sense that God and/or Chuck would therefore have been influenced by Amara in their time away together. We know how poorly an archangel was able to handle being exposed to Amara, so a human being exposed could absolutely lead to the maniacal egotist we saw as the main villain in Season 15. I see the Chuck of Seasons 14 and 15 as a corrupted Chuck using God's powers and pretending to be God in an ironic mirror of Season 11 where God pretended to be Chuck. I won't bog down this post with the details unless asked, but the story makes so much more sense this way.

Well, not always. Those first four, arguably five, seasons were amazing in the level of attention they paid to their continuity. It only started going off the rails in Season 6. The bad continuity didn't become a commonplace, almost expected, thing until Season 8.

Granted, that's like half the show, so it's understandable that someone might think it's always been the case.

This is the same writer who had a character go to heaven and then get resurrected by "Ezekiel" while heaven was locked down and inaccessible to souls or angels. He's definitely better about canon than a bunch of the Supernatural writers, but he's messed up before. (That said, I'm among those who think the canon departures are going to be at least mostly intentional, though I wouldn't be shocked if something slips by.)

They’ve said they’re going to reveal why things don’t match up in the season finale, so if they’re going the mind wipe route they most likely did just what you said. However, at this point time travel, reality warping , or alternate universe are probably the more likely answers.

I actually kind of like that except for the fact that Season 15 destroyed every universe except the one that Season 15 was taking place in. You could easily head-canon Seasons 6-15 as taking place in a different universe, but then that would mean that the universe of Seasons 1-5 wasn't the original universe, and it was destroyed in Season 15... (though you could head-canon that Jack rebuilt all of the destroyed universes after Season 15... but not sure how you could get around the Seasons 1-5 universe not being the original universe issue).

Always a possibility, but they have been saying in interviews constantly that there's a reason for the continuity not lining up and that they want to respect the original show's continuity. Doesn't mean the show is immune to bad writing, but a good number of the continuity issues are probably at least partly intentional.

He’s actually stayed with more projects to their cancellation than he has left projects early. But it’s a closer number than it should be.

It said that reapers are angels. But before this we were told that angels were separate creatures. In Season 4 we were told that angels hadn’t been on Earth for thousands of years despite reapers being around on Earth all the time. Furthermore we’re down that demons can possess reapers in Season 2, so if demons can possess angels, that drastically changes the trajectory of Seasons 4 and 5.

I’m pretty sure Season 9 was my least favorite overall. It didn’t justify Season 8’s cliffhanger, it didn’t bother to fully explore some of the more interesting things set up by Season 8, it would have opened up a huge plot hole in Season 6 if Season 12 hadn’t fixed it, Metatron was a thoroughly uninteresting Big Bad and Abaddon’s position/origin/goals weren’t explained well enough to set her up as a competent foe in need of such drastic measures as the Mark of Cain, the reaper retcon was terrible, and Season 9 just took the weakest plot lines of Season 6 and made them weaker (Season 9 had the less interesting civil war in heaven and the less interesting angel-trying-to-become-the-new-God storyline).