Skimmed the whole thread, wanted to avoid spoilers as much as I could, now at about 70% completion so I feel like I can chime in. Sorry if I end up repeating what has already been said.
This game has one of the best (maybe the best) art direction I've recently experienced. Graphics, mood, atmosphere, music (oh, God, dat music!), they literally hit each and every mark imho. I'd go as far as saying it quickly became a personal favourite of mine, again under the artistic standpoint. The vague souls-like exposition definitely lends itself well to such a visceral setting.
As far as metroidvania gameplay goes it's quite easy, although the combo system does allows for some nifty (if unnecessary, due to low difficulty) gameplay. Map markers are a godsend, my biggest gripe with Hollow Knight was basically being forced to map it by hand, to keep track of closed routes. I noticed that Blasphemous has much less backtracking than your average similar title, which is hit and miss really. I'd love to have a few more closed off areas to explore later on.
Since I've reached the final quarter of the game, more or less, and I've still found no popamole double-jump upgrade, I suppose no such thing exists, right? Incline if so. I'm all for experimenting away from what has started to become a formulaic game design. The idea of interchangeable relics that deepen exploration and open different routes is definitely a good one, I just wish they went a bit more heavy-handed on that, it's still one of the more linear metroidvania I've played.
All in all, gud gaem. Really gud. I will definitely be remembering this one for a long time to come.