https://en.wikipedia.org/wiki/Hyperion_(Simmons_novel) is a massive classic and is full of that stuff. The Matrix has The One die and be resurrected as a godlike glowing being.
Most atheists/Christians aren't as rigid as you imagine.
> a universe where there's no doubt that there is no god
The vast majority of scifi (and other genres) doesn't care or take a position either way. Nothing in Blindsight says "there can't be a God"; it has nothing to do with that.
True in a lot of cases but Simmons might not be the best example because he took such a bona fide ideological dive off a cliff later in life it even re-contextualizes the Hyperion books
I feel this is missing the point that OP is trying to get at. I wish I could cite Blindsight more accurately, but it's been a long time since I read it.
I don't think OP is suggesting the characters in the book sit down and reminisce about the time scientists proved there's no god after all, ha ha weren't all those believers silly all those years.
But Blindsight I found to be deeply nihilistic about the place of "humans as we know them". Whereas religions affirm that humans as we know them are somehow cosmically special due to their relationship with God, Blindsight posits they're just a weird blip of biology destined to be outcompeted.
I wouldn't necessarily call it atheistic so much as ahumanistic. It seems to focus on survival, power and force, and feels like it denies, rather than affirms, any sense of our own worth.
I may be overstating the case; again it's been a long time since I read it. I remember having, as some other posters have a said, quite a depressed feeling after having finished it. I didn't hate the book, but I didn't feel like I'd learned anything that would improve my life. Other than having had the chance to grapple with challenging ideas- which is better than having read something with no intellectual stimulus!
Religion aside, the imagery is undeniably cool. It goes hard.
No other reason is required.
Do you mean that the universe itself provides clear, incontrovertible evidence there is no god? Or do you simply mean that in the universe portrayed, none of the people happen to have any doubt about the non-existence of god?
I don't think there's any contradiction here. Atheists are often more interested in religious content than most religious people are, who just how with basics, vibes and traditions. Atheists (especially those that were raised in religious environments) are kind of morbidly fascinated with religious mythos.
PS: And i write this a somebody, who is forced by the enlightenment to admit that your fiction is the only one producing a lawful high trust society and thus should be the governing basis for a working society.
Consequently, I'm not really sure who the book is for. I don't know any Christians who like atheistic hard scifi (although, I exist so there must be others). And I don't know many people into hard scifi who really care for the religious imagery.
Personally, I find the experience to be unique, so I think it's worth it if you can get into it.
Besides that (and to spoil the point of the book) the biggest flaw is that the author doesnt seem to trust the reader to get the point, which is that consciousness is an unnecessary (and detrimental) evolutionary dead end. Real intelligence is totally orthogonal.
As a software engineer who has seen very intelligent systems with no more consciousness than a paperclip for decades, I got on board with the premise as soon as it showed up. But then I kind of had to wade through case study after case study highlighting the idea.
[1] - this isnt atheism that's aggressive, but rather a universe where there's no doubt that there is no god with all of the consequences thereof.