I think that the finale of Good Omens was... all right. Too rushed, while the second season was too slow and dragged out, with 6 episodes that could have been 3 or 4 - in hindsight, the events of seasons 2 and 3 would've been better served if each of the seasons had 3 or 4 episodes in total. But it is what it is.
Honestly, for me, season one would've been enough. I think that the story suffered without the source material, and the lack of Pratchett was felt quite keenly after the book adaptation part was done. Seasons 2 and 3 are much less whimsical, for one.
But then again, I am neither a shipper nor a part of transformative GO fandom, so what was all right for me is probably very lacking for those who were a lot more invested in Aziraphale and Crowley's love story.
If anyone is into more academic discussions of this, here is a link to an open access book dedicated to Good Omens.