this is to say nothing of

My questions are about the last sentence of the following paragraph:

"The idea that there are noticeable changes in style in art is not new to art historians. Indeed, Gombrich was influenced by his friend Karl Popper’s formulation of the ‘conjecture and refutation’ methodologies of science, taking the view that period style in art develops through ‘schemas and corrections’, with artists revising and extending the schema they have inherited. Alternatively, according to Harold Bloom’s scenario, they defiantly overturn the status quo. Such changes might be indicative of a number of factors and it would be impossible to make a thorough investigation into the reasons for this without taking into account the historical, geographical, social and philosophical context of the art in question, let alone the degree of its adherence to prevailing genres, schools or theories predominant at any time. And this is to say nothing of the changing perspectives of hindsight."

1. Does "this is to say nothing of" imply "let alone" and can it be merged into its previous sentence like this:

"...let alone the degree of its adherence to prevailing genres, schools or theories predominant at any time and let alone the changing perspectives of hindsight" ?

2. What does actually "changing perspectives of hindsight" mean here? Does it mean "different viewpoints that exist about such changes in art"?