You are right that the development of the game has slowed down considerably.
You might think you didn’t get “worth” of your money, and I can understand that (we are the first ones that wanted to make Gangs of Space a bigger game than it is now), but you can be assured that your money has gone 100% to the game itself, and to ensure we can keep the servers opened for the foreseeable future.
To be clear: we (Erhune & Grouroux) have made exactly 0$ by working on Gangs of Space for 6 years. On the opposite: we each put X0,000$ of our own money into the game, and took no salary for many years. The money that the game earned on Steam (and the pre-orders before that) have all 100% be put into 1/ paying the servers and the services to keep the game running and 2/ paying the other people who worked for the game (for example, our music composer Alex). I wish we could at least have drank one beer worth of our 6 years of efforts, but that has not been the case. I am not complaining of this fact (it’s a risk we chose when we decided to quit our jobs to try to make a game on our own). I just wish we wouldn’t be accused of running with the money, since that is very unfair.
(Also, just a minor nitpick, but we never received any donation. All the money the game has made has been in exchange of a concrete and playable game.)
Grouroux is working as best as he can to bring more players to the game, doing partnerships with content creators, and looking for external funds. Paying for ads or hiring staff members is off the table for now, the games does not make enough money for these options to be realistic in the current state.
I (Erhune) am still putting the time to keep the servers running smoothly, fixing critical bugs, answering support requests about technical issues, and keeping the session system running (remember: not making any money for this work). Unfortunately, I also have to spend the majority of my time working a real-world job, to be able to feed myself & my family.
I cannot make much promises about the future of Gangs of Space, except that we don’t intend to shut down the servers any time soon. As you say - the game might wither and die the slow death of forgotten MMOs. Or we might get some exposition from a few big Youtuber or Twitcher, which could make it feasible to hire another programmer to work on the game. Who can say?