Thanks!
I did not consider marketability at all when designing the game which I guess was the big mistake. I don't know what exactly would I have done differently, though. Coming up with something truly unique is hard. My art skills are quite limited, so I can't just choose a catchy art style and I can't and don't even want to outsource all the art.
The current art style divides people. Some like it, some absolutely hate it. The only comment on the release trailer was "looks like shit" :D
What the game really would have needed is some easily describable interesting "hook" that differentiates it from the mass. I could have then focused on this in marketing.
Besides that, the main problem is that I'm horribly bad at marketing or promoting my games or myself in anyway. I just absolutely hate it. I wasted a huge amount of development time by thinking about promoting the game without actually doing it, and feeling bad for not doing it. I hope that in future I can avoid this. After all, I'm not doing this for money and stressing about marketing sucks the joy out the hobby.
I don't have a new game planned yet. For now I'm just going to play around with some ideas and see if stumble upon something interesting. It feels refreshing to be able to start with a clean slate!