Sounds like one big security nightmare by a startup who wont have the resources to manage it all. Trusting someone else to manage your secrets is big mistake e in almost every aspect in life. Crystal ball says: Hacked, Bankrupt
Using open source/self-hosted secrets management tools can be a good middle ground that requires less trust while still providing secure sharing options to engineers so they don't resort to egregiously insecure methods. Disclaimer: I'm the founder of just such a tool - https://envkey.com (we're adjacent to Idemeum but are focused specifically on application-level configuration and secrets, not passwords or SSO).