Honestly, this looks like a horrible way to create software. The money and effort spent on the waitlist could have been spent on a minimally viable project instead.
The point of an MVP is to do the minimal to prove viability. A waitlist gives you an iteration of that in a tiny space of time. In OP's case they failed to critisie their MVP (marketing site and waitlist) enough. But if they had, they'd have only wasted a few days.