Speed is notable as someone who published no known poetry in his lifetime but left behind "about thirty unpublished and voluminous poems, plays, and treatises on subjects as varied as Pyrrhus, king of Sicily, Anglo-Saxon grammar, mushrooms, Methodism, the revolution of 1688, and Chaucer's Miller's Tale." (DNB). Some of his prose antiquarian writings seem, in the DNB's telling, to be of historiographical significance; no word on the quality of the poetry. In general, we can't know how many unpublished poets are lost to the historical record, so it'd be hard to know how typical Speed is.