How does one define mediocrity? The dictionary definitions include:

" The quality of being intermediate between two extremes; a mean.

(obsolete) A middle course of action; moderation, balance.

*, New York Review Books 2001, p.273:

In adversity I wish for prosperity, and in prosperity I am afraid of adversity. What mediocrity may be found?

(uncountable) The condition of being mediocre; having only an average degree of quality, skills etc.; no better than standard.

An individual with mediocre abilities or achievements. " https://wikidiff.com/mediocracy/mediocrity

But for myself mediocrity is the constant bombardment of "writers" telling other "writers" what, when and how we must write.