I watched "season 3" which is actually just one 90 something minute episode. Spoilers, if anyone cares...
It wasn't very good! Look, I never read the book, so I have no attachment to anything there. I liked season 1. Season 2 felt like a totally different show or it the whole thing suddenly became about nothing but the Crowley and Aziraphale relationship. I don't think this is what was intended, going by the first season, and my theory is Gaimain saw all the shippers going nuts on tumblr and decided to just lean into that. Whatever, they have good chemistry and I still thought season 2 was okay.
But this was so fucking rushed and random. OBVIOUSLY they had planned on six episodes but after Gaiman was exposed as a rapey fuck hiding behind a mask of "I'm SOOOOO progressive!" it was cut down to the length of two episodes. But you can't fit six hours of plot into 90 minutes. Everything just moves so fast with no room to breathe. Aziraphale doesn't even apologise to Crowely for how season 2 ended. They just team up again pretty quickly. There's a whole subplot with the car that was obviously supposed to be a whole episode that goes by in like ten minutes The whole plot with Michael makes no sense (why did she just burn the whole book at once? Crowley has a line saying she can't destroy it all but in the end only one page survives and that's because he pulled it out the fire.) We barely get any explanation as to why she's ending the universe. She was bored, or something. Jesus shows up and does ABSOLUTELY NOTHING. Okay, he learns how to play a card game. Great, but then he's earsed from reality with everyone else. God and Satan show up because they probably had that in the outline but Satan has no plot relevance either. Then the ending...
I'm not a SHIPPER but not even having Crowley and Aziraphale kiss definitely feels like "queer-baiting" to me. Yeah, they get reincarinated and end up together, but they're new characters now with no memory of everything they've been through before. I guess the idea is they came back human because they can't be demons and angels in the new universe. And all the humans just happened to come back into existence in this new universe too, exactly the same as they were? We don't really know, though, because we spend no time with them. We don't know how this universe differs from our own. Is it better or worsse? Does relegion even exist anymore if there's no God or angels or demons? Who knows, it all goes by in a quick montage. Show over! Terrible ending. The only scene that was kind of fun was when Aziraphale was disguised as a demon for a minute.
And that's the last Neil Gaiman show we'll ever see.