I liked the ladder analogy but I feel like this is basically every startup's experience. You climb up the ladders, invalidate assumptions when you realize what's too short, and identify traits that make some ladders better than others. And then at the end there usually is a big honking ladder than you realize is your best bet of trudging up and getting to 'the top.' If you can make the ladder exploration process one which you earn actual money during this time, this makes it a lot easier.

The OP mentioned 'founder-startup' fit, but I wonder what kind of startup trajectory they were expecting. Nothing is formulaic about a startup, but it sounded like they had close to the standard success case as possible. They launched a product, they got some customers, they got information from those customers, they realized future growth would require a pivot in their product but that growth could easily dwarf what they had done before, and... well, that sounded like a lot of work and they punted.

The Spaciety team launched a product, got customers, got revenue, and had a seemingly clear path to more growth via investment and product enhancements/pivots, so despite shutting down I would actually consider them a success. But I finished reading this and was mostly left wondering what trajectory the OP and his founders were looking for? Very few startups had a story like, "well we put in a lot of time to launch the product, got some customers, so now we just kind of hang out and let it run itself and we probably have a 50% chance to sell for like $3 million."

The OP talks about founder-startup fit, but were they a bad fit for Spaciety or a bad fit for starting a startup in general?