I think you and I simply disagree about your database being a core/critical part of your stack. I believe RDS is good enough for most people, and the only advantage you would have in self hosting is shaving 33% off your instance bill. I'd probably go a step further and argue that Neon/CockroachDB Serverless is good enough for most people.
Access control to your (customer's) data may also be a concern that rules out managed services like RDS.
I'm not sure what is meaningfully different about RDS that wouldn't rule out the cloud in general if that was a concern.