I'm familiar with it, but haven't played it. I'll try to keep your impression in mind, but to be perfectly candid, I haven't been too interested because:
a) Aesthetic/art style is an important factor that I'm very particular about, and I actively dislike the way it visually looks, how badly/amateurishly I feel that it's drawn, and how awkward and stiff the animations feel-- I keep hearing its animation praised, but I really don't get that from seeing it in action. The whole thing has a very fan-made feel to me in a bad way.
b) Me "loving" Metroidvanias can be a bit misleading. My general attitude about them is that I feel that 99% of Metroidvanias do it wrong and don't understand what makes the genre great (only a handful "get it", IMO). To give an idea, I weirdly love Hollow Knight DESPITE actually feeling that it's a pretty poor Metroidvania. I've heard Nine Sols described as "A Metroidvania that changes the mind of people who don't like Metroidvanias" and took that as a bad sign, personally (this is also what I heard about Prince of Persia The Lost Crown this year, which I did play and ended up disliking).
c) While it's been well received, it hasn't been SO well received that it's forcing me to give it a shot. I've watched some videos on it and didn't come away too impressed.
Maybe I'll give it a shot at some point, but pretty low priority