Individually authored masterpieces

1. Does "individually authored masterpieces" mean "masterpieces that do not have copies"?

2. Does "simply that" mean "but it simply means that"?

Text:

There are many works of art in the history of western art that are regarded as individually authored ‘masterpieces’ which were, in fact, patronage led and market driven when conceived and executed. Moreover, it may be argued that the expressive passion and virtuosity of the artist can be just as vital to this sort of art and that, while conditions of production and reception can be a constraining factor from the individual artist’s or even the individual consumer’s point of view, it does not necessarily mean that art made through the demands of the client or the marketplace is of a lesser order, simply that it has been generated in different framework of production and reception.