self-enforced mediocrity
Could you clarify a bit, what you mean here, please? As to mediocrity monopolizing, I know I do post an awful lot. Other than me shutting up, do you have any suggestions on how to improve the level of postings here?

Dear Jackie, all that is offered is generalised criticism. No suggestions for improvement, nor any explanation for the complainant's continued presence in this "closed preserve of mediocrity." If it really is such a waste of space, why doesn't the complainant go elsewhere? Just ignore the whinger.