So, I am finally playing this after I found it at a lower price and... there's a lot to unpack here. First things first, this game is objectively and undeniably bad. That's not to say I would not recommend it. It has some good fun and I have been playing it for longer than I expected.
But I guess to help people decide on whether to buy it or not I will detail this review further. In fact, this is the kind of game that makes it so easy to understand what works and what doesn't in a game. Because it has a lot going on.
Story
Don't worry, I will try not to spoil anything. But there's nothing to spoil here really. The story is by all means the worst aspect of this game and is not explained further than what you get at the first few hours. I don't know what the problem was, maybe they changed the story multiple times over the development, maybe it would not fit the gameplay, or maybe they just had no one qualified to write the story. It is very incomplete.
The story is full of tropes: the mystical orient, the amnesiac protagonist, the nature is good and industry is bad. While all of those can work, they don't here. Starting with the amnesiac protagonist. This is often used to make it easier to introduce the world to the player as it is reintroduced to the protagonist. It is cheap and overused, but it works. Or it would work if the game bothered to reintroduce it to the protagonist. But there's a lot the game doesn't say. Where was the protagonist before the beginning of the game? They were just... outside the playable area and even they don't seem to know. When did they lose their memory and why? I though it was after the only specified incident in their childhood, but the dialogue with one of the NPCs mention the protagonist did still live with them after the incident for an unknown amount of time, and yet they could not remember this NPC? Its so weird that every major NPC (and even unnamed NPCs) knew you as a child.
And spoiler alert because some might qualify it as one even though it is something you see in the first 2 hours: did the protagonist nonchalantly plant THE life tree as a child? If that's the case, it is shown to be a very trivial thing and it's not clear why it's so important to save it since it can be easily done by anyone and life existed before it. And why is the life tree being destroyed by the worldeaters in the first place? It is mentioned that they appeared because of the pollution, but the pollution was created at the human time and originated all the current life-forms a long time ago. So why is the world ending a second time now when it had clearly recovered and there's no new sources of pollution?
So, yeah, the story is a mess...
Battles
Now for a good aspect of the game. The battle mechanics are not the best I have seen, and they can be a bit unpolished and unbalanced. But the way you progress through melee, ranged and abilities is different and makes it more flexible since they don't need to conflict too much leveling up. You also don't have to be that good or highly optimize your gear. I have been able to use a very non-optimized clothing with no problem in battles just because I wanted the one that looked better even though it had half the armor of the other ones. I just wish they added more variations in combos and abilities.
Exploration
Another good aspect of this game. I found it fun to explore the world. They did manage to make it a very charming and even varied world despite the unpolished textures. The hazardous regions don't make a lot of sense, like small open regions that are somehow extra hot or cold or an entire region that doesn't have oxygen even though it's open and abandoned dilapidated buildings in this region can have oxygen inside. This only really makes sense for the radioactive and polluted regions to be contained to specific regions. But despite this, it is still charming and fun to explore.
Crafting
Because yes, of course they added crafting. In fact it is the only way to buy new weapons: you buy parts and craft them yourself. It works just fine. My only complaint is that it is too silly. Most of the parts are literal garbage. This is another theme of the game: upcycling. I get it, and I am all for upcycling. But you don't have to leave things rusty and dirty just because you are upcycling. The smiths in the game have literal forges but you don't buy reforged metal, you buy scrapped, rusty and often broken metal blades. Also, you can use a banana for a handle and a toilet scrubber as a blunt weapon... this game has a tone problem.
Binary morality
I though we all agreed this mechanic should be left to the PS3/Xbox 360 era. The way it is implemented is not a big deal to me, since it only affects who is willing to ally with you and very few powers. It is not game-changing, but it is annoying. People often complain about the narrator, but I somehow tolerate it. What is really annoying is having every dialogue stop when I make a light vs dark decision so that the inner angel and demon can have their little exchange... I am not kidding, you have an inner angel and demon and they will appear every single time you make a moral decision to mock each other. It's three to five lines of dialogue every time.
Narrator
Speaking of the narrator. You have one. People hate it. I get it, it is a strange decision. But somehow I feel that its this game's THING. At this point I cannot play biomutant without the narrator (there's an added option to remove the narration). I won't deny it took me some time to get used to it, tho. But it was weird not having it on since the creatures talk in gibberish and are translated by the narrator. If you remove the narrator the dialogue is still just the subtitle for that narration and it feels off.
World building
While not complex, I have a lot of praise for one aspect of the world building: the vocabulary. It is often ignored that a non-human sentient being would have its own way of naming the world around them. They made an entire new vocabulary that is actually easy to understand. New words for mom and dad, often descriptive ways to name your gear, basing much of their naming of objects on the sound or most pronounced aspect of it. It is charming, and make the creatures less human-like.
Last considerations
The game is meant for a very young audience... I think. I actually did not have this impression looking at the trailers, but playing this game it does make me feel like that was their goal. That would explain the silliness and weird decisions such as including the narrator, the angel and demon, the reductionist view of nature vs industry, and the tone problems.
TL/DR.: It is an objectively bad game, full of strange decisions, but it has a lot of charm and can be very fun to play. Just a heads-up, on the base PS4 the frame rate drops frequently.