I think you hit the key word: accessibility. (IMO) If you have a tangled API, whether via the language or the library, people will be more hesitant to contribute because it cost more time and requires more complete understanding.'
I think it just rehashes the idea that OSS projects are easier to grow if they are are small and in popular languages.
I've seen a project structured non-ideally for the technical task, but that enabled users to quickly find and understand the part of the project that would fix their problem.
It ended up being like the pyramids, constructed with thousands of labourers. But very successful - effective and popular.
So perhaps ideal contributor structuring is more important than ideal technical structuring...
I think it just rehashes the idea that OSS projects are easier to grow if they are are small and in popular languages.