Yes, I thought so a bit at one point, but a) he’s reasonably egalitarian in whom he mocks, and actually, monotheism seems to be very low on his list of subjects for satire, and b) he seems to be more of a skeptic than an atheist, like he wouldn’t commit to totally making fun and he did have some respect. The one thing that I think he thoroughly made ridiculous was polytheism, but he’s made fun of practically EVERYTHING. Including, if I remember rightly, some form of atheism, but yeah.
Honestly, though, I feel sometimes like his satires are so satirical they cease to be satirical and then kind of sprout lives of their own, kind of as separated from the real religious beliefs. I’m personally quite ready to believe that the Discworld just has some really weirdo gods swooping up there, but that’s because after a while, when you think of it as a satirized Earth, the satire gets so heavy that you realize- there’s a total disconnect from the real thing.
But most of all, these are Pratchett’s books and the entire point of sci-fi and fantasy is that the author can invent his/her own world. If you want to read, it, do, and if not, don’t. Remember, this is HIS world- YOU are an intruder :).