itch.io

How is realeasing a demo "fraud"? 
As you said yourself there is nothing you can buy, so what is being misrepresented or what are you being cheated of?
Releasing demos before a product is released is in fact very common and usually done to gather interest for said product.

Demo means test version

Releasing  a demo for a game that is still in development is totally normal. Wishlisting games on steam is a huge help to developers, and letting people try the game before they buy it is a consumer friendly way to encourage people to do that.

Nothing fraud about releasing a demo before the final product.

If I might suggest... here's some gaming topics which are much closer to (if not actually) fraud which your anger would be better suited towards:
(In no particular order)

• Paid Alphas/Betas/Kickstarters which never get released.
• Gambling with tokens/gems/etc bought with real money.
  • Especially when it's aimed at children or gambling addicts.
• Forced online connectivity for single player games.
• Games with Bitcoin/Cryptocurrency.
• Games with Gen AI.
• Kickstarters which have a reward to "let you help develop the game"
• Games which you own, but can't play because the publisher/devs pulled support.
• Games which you'd like to own, but can't legally buy because the company which holds the copyright for the next 75+ years won't sell you a copy.
• Games with Day-1 DLC or patches.
  • Especially games with Pre-Day-1 DLC.
• Game reviews/reviewers which:
  • Do not disclose that they got a game for free.
  • or, Do not disclose that they received other compensation related to the review (ex: All expense paid trips, catering, special early access, in person meeting with the devs, etc)
• Game Companies which put devs through crunch.
• Game Companies which fire entire teams after record sales.
  • or, after just buying the teams.
• Game Companies when they sell you stripped content as DLC.
• Game Companies which sell you an old game for substantially more than the original cost.
• Games that you pay full price for, but you only get a ~License~* to play.
• etc etc... 
  • I've got to stop here, or I could be at this all day.

* There's ALWAYS "fun" asterisks and restrictions with ~Licenses~, like when and where you can download the game, what device you can play it on, etc etc.