Review as of version v0.21.29
So far it's a great take on the formula popularized by games like terraria, with the twist of this game playing on a 2.5d plane instead of beinga sidescroller.

Also, the game has a very light town management system, where you can recruit villagers that can do certain things like tend the farms, the animals, chop trees or fish, among other things.

I have a couple of hours in and it has been pretty enjoyable!

(review reflects v0.21.28)
Necesse has a ton of potential, and I can see it being a fantastic game that even comes mildly close to being as good as Terraria is one day. Unfortunately, that day is not today.
The game is built around bullet hell bosses, but you barely get any mobility (as far as i'm aware you get speedy boots and a dash item that you either manually use in your hotbar or replace the speedy boots with to use). This can lead to some incredibly frustrating moments - for instance, the pirate boss due to the infinitely respawning minions and the boss's strong attack leaves it as "hit the boss once, dodge away, repeat 500 times, then try your best to run around until you can pop a healing potion".
The housing and NPC system is neat, but as of now it feels pretty barebones. The Elder is the source of progression, and the only NPC who offers quests. There's a few NPCs with exclusive(?) automation bonuses, but really all you need is a farmer and some NPCs chopping down trees and you'll be good. The main con for not having good setups with your settlers is shop prices going up, but none of them really offer anything worthwhile to make you want to buy from them anyways.
The settlement system also begins having negative effectives for crowding the second you hit 6 settlers, going up in severity every 5 settlers, regardless of how far apart the houses are spaced or how much land your settlement actually takes up. While this feature seems like it's trying to encourage setting up settlements across islands, that's annoying as hell. You don't get a fast travel system for settlements set up until around 10 hours in, and even then you'd have to make sure to set each settlement up with enough settlers to function on their own, storage, etc. and constantly have to hop between them to grab items or to protect them from raiders.
It may be some weird multiplayer balancing thing, or maybe I just suck at the game, but it feels like enemies are way too annoying. By the time progression led me and my friend to the swamp area, with the best armor we could get at the time and the strongest weapons we could grab, we were still constantly having to be on the lookout as a single enemy could hit you twice and force you to hide and wait for a potion cooldown to end.
The progression system is also kinda boring. Quests boil down to "go to this biome. kill this enemy until you get an item. come back to the settlement. go back to the biome and go kill the boss. go to the next biome. repeat over and over again." It'd hurt less if you could just go to the next quest automatically, or if it just cut out of the middleman and left the enemy drop rewards as alternate quests from other NPCs, but nope.

The main positives for Necesse that I see is that it has a ton of potential, multiplayer is incredibly easy to start (like Terraria), and there's room for some very cool mods to be made (such as the WIP Necesse Tech mod that seems to be setting up to be similar to Minecraft tech mods)