I don't know anything from painting and never thought about painting or buying paintings so I don't really have any context. Is the main antagonism against this phenomenon that:
a- It's not local?
b- It's not one of a kind / unique?
c- It's of lower artistic production quality?
d- There's deceit?
From my rough uncultured perspective, if I ever somehow thought I wanted to decorate my home and went out to buy something, only (c) has any real meaning I'd think.
In other words, is it ok if I'm eating a banana from somewhere that can grow banana en masse rather than a banana grown in my backyard?
If not, are people mainly objecting to the fact that the mass produced bananas are inferior (and this is true more often than not) or is it because of other reasons.