I would use Oracle as a counterexample - while it's very stable, and there is a feature for everything (only some of them are in various extra $$ addon products), however, I was really surprised at the horrible quality and dev-unfriendliness of all the tooling and ecosystem compared to the equivalent open source tools; and the brittleness of their integration with any non-Oracle products, which is a necessity in many larger companies.

While there is a lot of quite good proprietary software, and Oracle is good in many aspects, I would not really call Oracle best in class; in so many situations PostgreSQL would be preferable even if you ignore Oracle licencing (and you can't really ignore Oracle licencing).