There are a lot of good things about this game, but a handful of problems that make me not want to play it. The steam hours doesn't actually reflect the real hours I played because I went into offline for it to stop tracking so that I would have the option to refund it still later.
One is the secret/challenge system. I think having a large cut of content behind secrets that most people will have to end up googling the walkthrough for is just bad design. Especially because you literally cannot know what the challenge for a level is until after you've beaten it. So if you are the type of person who doesn't want to rely on guides, you'd have to write it down and play again.
Another is the general lack of content. This is partially because it is early access, but still a detriment to the game. Not enough variety of guns, enemies, etc.
The graphics are surprisingly not a major problem. This is a big turn-off for most people, and while I would certainly have preferred a better looking game, it's ultimately not something you notice most of the time. In actuality, graphical design is a bigger issue, it can be hard to discern things apart at times because of the design of levels, enemies, and objects, and the low fidelity of the textures only makes this worse. Turning on PSX mode, which I would normally recommend because it makes the game look nicer in a retro way, makes this problem even worse.
Ultimately I think this game is not bad by any means, but I didn't play it for very long before tiring, and I definitely think it doesn't deserve such a high aggregate rating.
I think I might like to revisit this game in the future on full release, that is, if it doesn't burn out like many early access titles if/when they release.

Post Script: I didn't expect to get a dev response, so I feel compelled to defend my statements
First, in 1-3 there was some parts of the stage and a boss that I could only fight by trying to complete the challenge to beat the secret encounter (this is the game's own words). Considering that this game is essentially just going through levels killing things, I cannot see how you could possibly construe this "secret encounter" as anything but content hidden behind a secret/challenge.
Not convinced? There's a gun, the slab revolver, that you can only acquire by finding four secret slabs across four levels.
Having read a guide, I would actually agree that most of the secrets and challenges are of a reasonable difficulty. This doesn't change the fact however, that I greatly dislike it when games include a secret/challenge system that rewards you for anything more than collectibles or clout. As mentioned before, there are, at times, parts of the game that you simply would not encounter without completing the challenges.
The dev's explanation for why you only see challenges afterwards is fair, and I accept it.
Finally, the Enemy Silhouettes option is ultimately a band-aid solution for a problem that the game itself creates. It's a good option to include, don't get me wrong, but ultimately doesn't change the fact that the graphical design necessitates it in the first place.
I would like to re-iterate, this is by no means a bad game, but it's not for me. I'm offering a balanced perspective on some of the negatives for this game so that people can make an educated purchasing decision. If none of what I said bothers you, go buy the game, you'll probably like it. But if it does bother you, it's better that someone had provided you that information.