DevRel and communication are full time jobs. If a open source project is depending only on volunteers it is hard to maintain communication at steady level.

Not everyone can be a good communicator. You can learn communication skills, but sure it helps if you are an extrovert and not introvert.

Who knows better than developer how developers think, how do they operate, what do they expect from products?

Look at it from this perspective, can you learn a marketing person developer skills? You could but there is no need. He heeds to understand the facts about the product, target audience, technology landscape, etc.

I personally think that the core ov the DevRel team should be developers that know the developer community. And then you build upon that.