> But in reality the language as severe impact on how the ecosystem can and will develop.
This so much.
One, often omitted, property is also simplicity of the language. If the language is straightforward, then there's a much larger audience who can be potential contributors.
Being opinionated in code style is also if value, as it's easy to contribute to others' libraries.
It's one of the reasons I think why Go did quite well as far as quick library ecosystem creation goes. It's fairly simple, at least as far as the basics go, and diving into/contributing to third party libraries is very easy, due to opinionated tools like gofmt and the overall language simplicity.
Whenever I need something in a library that's not supported yet, I'm able to achieve it in less than a few hours, by quickly diving in and making the changes, even in an unknown codebase. The magic is that this works for the vast majority of libraries.