Source of Madness

Good, not great. It's a rogue-lite, procedurally generated game without much variation. I think some monsters and bosses are random, but a lot aren't. Also a lot of levels variation isn't really relevant, its just variation without much actual effect. Compare with Sundered that makes the bite sized chunks interesting to traverse versus this. It doesn't help that by default your movement speed is on the slow side.
I love the style of the game (Gustave Doré-esque) and the combat is fine pretty good even if the dash gets a bit sticky sometimes. Generally you'll fall into a decent build pretty quick especially once you learn what everything does. I went with arcane damage and cooldown, using King's Rings and Arcane Bursts almost exclusively from start to finish.
It's too long per run, with levels like the caverns being tedious to explore. You'll have seen pretty well every variation after a few runs. The tower of knowledge is ridiculously large, just to explore for NPCs who say the same thing every time even after you complete the 3 Acts of the game.
From there it's a rogue-lite, meaning you gradually get stronger. The issue for me is the left upgrade tree makes more items drop and opens up more classes. This just dilutes the pool of weapons and classes I want. You can set their drop rates to low but it still adds more that I don't want compared to what I want.
Now that I've beaten the game I just need some more boss blood and to be poisoned a bunch of times before I've 100% it. Except for killing 10,000 monsters which is an obnoxious amount.
Pro-tip: In the forest there are red rings that sometimes spawn which continually teleport in monsters. With precision weapons (like King's Rings) you can farm at a rate of 30 per minute or so. At the very least get a bunch of money from them before killing the ring.
Main criticisms:
Story is severely lacking despite being able to draw upon the whole Lovecraft Mythos. See Hades and Rogue Legacy 2 for effective rogue-lite storytelling.
Physics engine. Pardon me but I wasn't finished with those monsters that shot into the sky, and I'm sure they weren't done with me.
Level length: too long, too winding in many areas. Also no maps. The more linear levels are generally about the right length.
Item and monsters sometimes spawn in solid rocks. Not often but enough to be noticeable and fixable.
The randomness adds little, if anything, to the game. It rarely makes encounters interesting. Again, see Hades or ScourgeBringer for meaningful randomness of encounters.

I think a lot of the negative reviews are being a bit too picky. Carry Castle is a one-man development studio, and they're trying to do something pretty cool. I think we should be generally supportive of such efforts.
The AI generated beings in Source of Madness are quite possibly the closest we've gotten to the unintelligible madness at the core of lovecraftian cosmic horror. AI is particularly suited to this, since it is, well unintelligible, having no actual connection to logic. I wouldn't accept AI being involved in any other game, but strangely, it works here.
It's a bag of jank, to be sure, but it's fun and intriguing. The crazy things still manage to pop out at you with one, none, or 1,000 legs. It works.

The game is a mix of both good and bad, with elements that seem to clash. Instead of calling it simply bizarre or alien, I think terms like 'chaotic' or 'confusing' better describe its nature. It feels like a glimpse into true, indescribable madness that resists easy explanation. I believe it could have been much better with just a bit more refinement and focus.
어쩌면 이런 것이 형언할 수 없는 광기인걸까.

yes with asterisks.

Simply put, the game has a vibe in terms of aesthetics and feel that can make people overlook the flaws, as I did.

this is essentially procedurally generated, sidescrolling, roguelite, lovecratian Diablo
if any of those words are red flags, I wouldn't get it.
I like lovecraftian stuff, and the gameplay isn't bad, ergo, I like what I'm playing.

Yes but wait for a sale. I doubt I’ll play enough to get the full value out of it. It feels like a roguelike diablo-esque metroidvania, despite the lack of backtracking typical of a MV title. The concept is neat and it’s a good use of AI (to randomize enemies and maps), with good progression and multiple classes. May be a tad too easy for some. If you love Lovecraftian themes, this nails cosmic horror and fleshy enemy masses.

I don't like this game. but it's not bad enough for me to give it a bad review

I am no soulslike/metroidvania/roguelike officionado. This game is sort of like if Noita was written by HP lovecraft and someone on the team was perversely obsessed with procedural generation. I love it. You do casting, not melee, and your spells are things you spam, with low cooldown. You avoid being killed by monsters by hiding in their hundreds of armpits, looking for when the telegraph that that armpit will start emitting poison gas. I wish the time taken to restart a game was lower because I die every 5 minutes.