This is an art-oriented voxel crafting and building game, whose entire focus is acquiring different resources in different colors to sculpt and build whatever you want on land that you claim.

The Good:
The ability to change blocks into different shapes, a dynamic colored lighting system, and a small handful of mesh furniture/decoration objects allow you to build more detailed structures than default Minecraft.
A portal system that lets you seamlessly move between locations and worlds (planets with different resources), and a surprisingly entertaining grapple maneuvering system both make getting around fairly entertaining.
There used to be a fairly technical community that made websites, scripts, and tools to help with shopping, finding materials in specific colors, and looking up crafting recipes. This same community made some pretty breathtaking builds you could explore through player-run portal hubs.

The Bad:
Unlike Minecraft, there is really nothing else beyond building. Exploration is limited because planets are finite looping spaces, and there is little incentive to do so. There is no sense of progression, story, or really accomplishment in repeatedly farming monster spawning 'meteors' to get resources. There is no 'endgame' beyond just building more things and stockpiling resources - that themselves create a burden in terms of how to store and organize it all.
UI, storage, and quality of life issues become apparent after extended play. Large emphasis on real-time waiting for crafts and grinding the in-game currency to expand builds beyond a certain point.
Land claims by temporary players during free weekends - even single day players - would persist for several weeks and could not be moved until they expired. This led to a landscape dotted with temporary cube houses all over the place.
Player-driven economy and competition could be cutthroat and predatory. Systems to generate wealth based on people visiting your land were twisted into moneymaking schemes for a relative few people who ran the 'big' cities, shopping malls, and portal hubs, which led to lots of toxicity and greedy behavior.

The Ugly:
The game has been abandoned in place, existing now only as a hole for people to throw money at perks that automatically refuel your build claims so they don't expire, or for people to pay to maintain custom planets that will be forever gone if payment lapses too long.
The prior devs had grand promises for patches and expansions, new content, etc - but also complained the system itself limited them from adding more block types or adding requested features. There have been so many cycles of promises and claims that went unfulfilled, that there is no real hope at this point a meaningful update or re-engagement on the part of developers will happen.
The game HAD a community once, which was mixed but became more toxic as time went on. Admins were absent, allowing in-game trolling to occur - walling in builds, harassing signs that can't be removed, abusively exclusive claims to resource hotspots, etc.
The devs also artificially locked certain colors away, even from paid planet creation, seemingly out of spite. This is a pretty critical shortcoming in a game whose whole purpose is getting blocks in colors to build!

The Final Word:
This game was only ever good if you had an active group to build with (that manages to avoid drama and personality conflicts over resources, land claims, etc), if you were able to create goals of your own to work on when the game doesn't really give you any, and if you were willing to sink lots of time into grinding and acquiring the resources to finally build whatever you wanted to make. If you got bored, you either had to keep logging in periodically to 'refuel' all of your builds, or you had to pay money for the game to do it for you, or you let everything vanish. The game had a chance to start from 'better than base minecraft' roots and then incorporate new content, but it never did so.

Fun at first but too grindy and boring. There's no one to play with and the game is made so you have to play it multiplayer

Boundless is a phenomenal building, exploration, and economy game that I'm surprised to have only recently discovered!
It makes many improvements over other voxel building games (e.g., Minecraft, Trove, 7days2die) such as chiseling, which is used to shape boring cubes into interesting shapes such as traingles, slopes, and lattices. And most blocks come in 255 different colors-- which can be very fun to collect!

What truly sets this game apart is the player-driven economy. I spent my first day of gameplay exploring the portal networks, which are used to hop between worlds, while writing down the location of my favorite player shops. My second day was spent buying and selling between shops, flipping goods for profit! Within my first few hours, I made a tidy 30k profit from simply buying and selling raw meat. That was enough coin to afford a full set of decent tools and machines.

I'm now 74 hours in with a maxed out miner and a crafter. My next character/skillset will be a hunter (which allows going on "hunts" used to collect rare materials to sustain portals between worlds). Now that I have plenty of coin, I'm about to begin my first major construction project, and look forward to having a shop of my own some day.

There's some negativity on Steam and the forums which I personally don't understand. The game seems plenty active to me-- 50 concurrent players seems to be more than enough to sustain a working economy and group-based events called hunts. And folks seem friendly and helpful. The developer doesn't appear to be making any new improvements to the game. I'm not mad about that. Maybe I'm an outlier, but I actually prefer infrequent updates to finished games-- few updates means that players can build their worlds and even mod the game (mods are limited to UI improvements, afaik) without worrying that some change will disrupt what they've worked so hard to obtain.

Loving this game so far. I expect the next couple hundred hours to be even more enjoyable.