I've found that contracting to just do the work to build peoples ideas, getting your paychecks, and maybe a tiny bit of equity when you can negotiate it, is a safer long-term bet than any founder/co-founder experience.
It's unfortunate when self-declared founders think they just need a developer to 'embody' the product they dreamt up... it's also unfortunate when the dev who is the one capable of delivering a product lets themself be treated like a cog instead of acting as a driver.
It sounds like the CTO should have been hired as a tech trainer for the existing CTO == you.
I see it again and again in early enterprise. When a dreamholder feels underpowered at the real task of delivering product, thdy build layers of admin to lower the product delivery team, burn through CapEx and OpEx and label that 'growth' and eventually the % promise is worthless.
Production teams beware of founders who just need a dev and not a team of partners. Ego > Ability & Manipulation skill instead of leadership capability.