No one says this is a beta, they're calling it an alpha.
You've got that completely backwards. It's true that this does give publicity and marketing for the game, but a demo would be highly polished and fixed up nicely. This is not, and does fit the definition of an alpha/Early access title.
Yes, there are more areas in the game that are done, yes Larian is holding them back, but they do have plans to release more areas later on. Right now they're working on ironing out a bunch of the major bugs and glitches.
If you do not want to help Larian to find and squash bugs, or do not want to give your feedback about how you'd like to see the game work, then certainly, do not buy this game and wait for the final release.
Larian is an indie dev. Maybe a large one, sure, but an indie dev nonetheless. They've abandoned traditional publishers and are publishing the game on their own. That's sort-of the definition of independent.
