First of all, thanks for sharing your story. I think the real lessons here is that:
- a founder CTO needs to be very strong on product: I never accept offline capabilities or even mobile compatibility for a MVP, this is simply never necessary to get the needed early feedback
- as a tech startup cofounder, your infra should be a docker-compose.yml and that's it, your CI should be a README "ssh, git pull, docker-compose stop, build, up" and it should take max 3-4 hours to set up
- caring about unit tests and the like is useless when you're still iterating fast, automated tests are good once the product is stabilized and you want to kinda "freeze" it or at least stabilize it and introduce some friction in the dev process to prevent regressions (you trade speed for quality)
Sounds to me you spent entire months working on things which did not provide any business value