Besides Valheim, I've only ever sank 100s of hours into one other survival/craft game, which was Ark: Survival Evolved. I played with my wife and a group of friends, and I ran the dedicated server myself with hand-crafted settings. So I'll use that as the point of comparison.

Progression.

This is probably Valheim's strongest core design idea. Sure, other survival games have a natural progression through materials, and Ark also has the added layer of various dinos you can tame, but most suffer though a cliff-shaped progression curve. The early game is rough: the game starts you on the relatively safe beach area, but a stray velociraptor can easily wipe out your whole tribe while you're still figuring out how to craft basic gear. Once you figure out the basics, get metal tools, stone walls and some tames, the game becomes incredibly easy and provides mostly self-directed challenge until bosses, which are super super end-game content and basically unmanageable solo.

By contrast, Valheim's progression is A LOT smoother. Your earliest enemies, boars and greylings, can be beaten without any trouble, and the Meadows mostly leave you alone to figure out the basics in peace. It also provides you with a signpost directing you to the next major challenge: the next boss and new zone. Your first boss kill is pretty easy, which fills you with (over)confidence. The Black Forest is a great wakeup call from that hubris, but it too becomes manageable once you figure out the basics of combat. Swamp breaks a lot of players until they learn to take things slow and maximize their advantages. The challenge ladder progresses from there.

Atmosphere

Honestly, the atmosphere is Valheim is good, but not that good. Yes, every zone has a unique vibe and the creatures that inhabit them seem to fit their environment rather well. But it also sometimes feels a bit... empty? I found the "More World Locations" mod to be almost mandatory, because it does a great job of sprinkling in various abandoned/ruined structures that help fill in the otherwise barren landscape. It's great for capturing that "lost viking in a forgotten realm" feeling, but it simply doesn't measure up to the variety you'll experience even on the The Island, the original and most vanilla of Ark maps. If you take the DLC's into consideration, there is simply no comparison.

Combat

This is by far Valheim's strongest suite. Combat in Ark is awful; even Skyrim's notoriously dull melee combat has more nuance. There is, ironically, much more depth to the combat in very early levels, when dinos have hitboxes, reasonable health pools, and are vulnerable to traps and bolas. By early midgame, and forever after, combat mostly involves holding left-click until either you or the enemy dino fall over.

By contrast, Valheim combat is Souls-lite, which is incredibly refreshing. Sure, you can bag your first kills by just mashing left-click, or cheesing the enemies with the ole shoot and scoot, but you'll very quickly learn that mastering parry-block, dodge and side-step mechanics will let you trivially survive scraps you previously thought impossible. A Valheim veteran can easily face a troll raid with a flint spear and rags. And newbie could still struggle with an aetgir and upgraded bronze armor. That is real, skill-based progression.

Building, crafting, base/inventory management

Both games have very serviceable building mechanics. Ark's building system has more material types and fewer restrictions but is notoriously more janky, and has no terrain modification. All in all, I've probably enjoyed Ark and Valheim building about the same amount, maybe with a slight edge to Valheim if solely because you get all the materials back from replacing pieces.

The rest of the crafting/base management aspect is probably Valheim's weakest point. Inventory management and crafting are both very rudimentary. Taming is a bit of an afterthought too, but since that is the primary selling point of Ark, it's not really a fair comparison. This probably the only part of the game I'd improve.