It is well supported by the Django ORM (and the Django ORM is fantastic, especially migrations-wise)
It is ACID and conceptually correct
It has all the features I ever needed (full text search, fuzzy matching, constraints, materialized views, ...)
It is very widespread in managed database services (DigitalOcean, AWS, GCP, etc)
Despite what the Uber monkeys think, it scales
It has plenty of convenient types (arrays, hash maps, JSON) that let you be very flexible with how you represent your data (even get the flexibility of NoSQL when you need it)
And of course you can index and query those types (yes you can make an indexed query deep into a JSON field)
PostgreSQL is my choice because
All good reasons I can see why its so popular now looking at all of these responses.