You could also just have worked on lowering those overheads in PG, just saying. It's easy to blame "PG devs", but most of us could get changes quicker to our company's respective customers by just fixing everything in forks.
We would be happy to contribute to PostgreSQL, but I think the issue here is that, as a business that is focusing on a very particular use case, we are not perfectly aligned with the PostgreSQL roadmap. We want to be able to move quickly and adapt to customers needs, focusing on the pain points and issues they have. This simply isn't compatible with the more conservative development pace that main PostgreSQL understandably has.
From another perspective, I think one strength of PostgreSQL is, in fact, its support of extensions, enabling innovation alongside main PostgreSQL while the core developers can focus on a rock solid and extensible foundation. So, from where I am coming from, this is a feature and not a bug.