Valheim is an Early Access game. Let's take a look at Steam's definition of Early Access, shall we?

What is Early Access?
Steam Early Access enables you to sell your game on Steam while it is still being developed, and provide context to customers that a product should be considered "unfinished." Early Access is a place for games that are in a playable alpha or beta state, are worth the current value of the playable build, and that you plan to continue to develop for release.

Releasing a game in Early Access helps set context for prospective customers and provides them with information about your plans and goals before a "final" release.

So, is Valheim complete? No
Did they claim it was complete when they released it? No
Did we, the consumers, purchase the game knowing that its state was currently incomplete? Yes
Is the game in a playable state? Yes
Is the game fun? Subjective. My answer is yes, your miles may vary.
Is the game currently being worked on? Yes. They are working on the next zone, Mistlands, and keep people updated as to the progress.

So, the developers have not cut and run. The game is exactly what it says it is, an early access game that is currently not complete. And for a small development team, they're doing a better job than some AAA companies who have all the money to throw at their projects. Even if the game never completed, I'd say almost 250 hours of gameplay has more than compensated me for my $20 purchase. How many other forms of entertainment can say the same?