why do so many people seem to have a hierarchy allergy round these Western leftist parts
The stance I've arrived at is that hierarchy in a broad sense isn't bad, but rolling all of the powers into the same hierarchy is.
No one is going to be the best or the most insightful or most apt at everything. Also, spreading out parts of the roles not only allows more people to distinguish themselves, it makes transfer of power easier and reduces your vulnerability to decapitation approaches.
Someone's going to be the breaking wave crest, but we can still all be water.