Dude its free
Even compared to other indie / small developers this is low content. Thee are a ton of free web games that have more content: Epic Battle Fantasy series of games. GemCraft series of games. Cookie Clicker. Cursed Treasure series of games. Stellar Squad, Kingdom Rush series of games. Rebuild. Creeper World series. Also there are many small / indie developers who have made paid games with more content: Terraria. Stardew Valley. Night in the Woods. Oxenfree. FTL: Faster Than Light. The Binding of Isaac. Deeponia series of games. Celeste.
You can go down the list then: there are literally thousands of games out there that charge as much as or higher than From Orbit that don't even have half as much content. Go rail on them.
You should also only be referencing games that were made by one person. Deponia was made by a 90-employee company. Not all devs can be one-hit wonders like ConcernedApe behind Stardew Valley, nor should they be expected to.
That said, I agree that From Orbit is overpriced for its content. I thought the black hole at the end of the system map was just one segment of eight, but that was the end of the game. So, I'm glad I was able to play it at no cost, but I'm also not complaining.