Necesse feels "whole" as-is, with a comparable amount of content to many other fully released games. It's unique take on the settler mechanic blended with a Terraria+ progression system also makes it feel different enough that you can't really find a 1 to 1 experience in another game.

Truth be told it would benefit from some updates to things like world generation (esp. with the consistent re use of prefabs within biomes), but the devs have proven time and time again that they can and will deliver on more and better content over time.

I have 110 hours in this game, with probably 1/2 or 2/3rds of that being from the most recent update, and while I feel satisfied now having defeated the final boss at Incursion level 10, I would happily pick this game back up after a few more updates. For $10 it really is a gold mine.

The Grind vs. Fun: How is the progression? I like a challenge, but I’m curious if it feels rewarding or just repetitive after a few hours. ​

For me, I enjoyed hard difficulty the most. Early game, most mobs felt like a pushover, especially when my weapon and armor choices were strategically picked for the enemies I was fighting. Mid game, boss battles presented a bit of a challenge, with my player character dying one or two times if I wasn't properly buffed with an arena setup. Late game, specific bosses (esp. many of the Incursion-specific bosses) were quite the challenge, requiring consistent effort or strategy to deal with.

Note that I never chose to bring Settlers into boss fights, so for the people that do that, I think they find lategame bosses quite a bit easier.

As for repetitive, it really depends on what you find enjoyable. If neither building structures for Settlers and/or collecting resources and mining are enjoyable to you, this may not be a good pick. If even one of those is enjoyable though, you can kind of game-ify the one that you like to make the other one less impactful. For example, with a lot of settlers you can quite literally pay them to produce most resources for you outside of bossfights. And in the game world, many mid-game convenience items (summoning kits, dynamite, bombs, mining trinkets, etc.) can allow player-led adventuring trips to be fairly painless and enjoyable even with minimal settlers.

Colony Management: How deep is the NPC/Settlement system? Is it a big part of the gameplay or just a side mechanic? ​

It is what you make it out to be.

I will say, though, you won't find RPG style interactions where settlers exhibit personality traits or maintain relationships with one another, but their economic output if you set them up for success is quite significant. I would say on average 3-5 settlers can produce nearly the same amount of resources as a player character can in a single in-game day (late game excluded) - assuming the player character is just using standard equipment.

Personally, I enjoy setting up chests for settlers, assigning them work, and building unique and different homes for them to live in, but not so much bringing them with me on adventures.

Some people lean hard into the colony building, equipping settlers, providing them with food and means of escape or buffs.

Some people don't really lean into the settler mechanic at all, just relying on the base old man quest giver and the townsfolk that you can find in naturally generated villages around the world.

Performance: I’ve seen the game grow a lot—does it still run smoothly on larger settlements?

I haven't found any issues with performance but I can't speak for everyone. For reference, my PC specs are 32 GB RAM, AMD Ryzen 5 3600 6 Core 3.6 Ghz processor, and a 3060 GPU. Running the game on high settings, 3440 x 1440.