I think Postgres is great for many of the same reasons that people often (wrongly) tout NoSQL systems for. It's flexible, featureful, simple and quick to get started. And unlike most NoSQL systems, it has full ACID compliance and can scale well past MVP stage to the point that most businesses will never hit its limitations.

If you do hit really huge scale then you will need to start looking beyond Postgres to solutions like Cassandra, Scylla, etc. But hopefully by that point you have a large dev team capable of handling the extra complexity.