well it kinda goes without saying that the very best art is both unique and high-quality
the alternative viewpoint would be that original artists with mediocre execution of ideas can inspire said perfection in others and therefore further the art in a way that simply quality alone cannot
that's without considering their intrinsic value too. identikit 7/10 albums bring nothing new to my life and i delete them all the time, but if i come across a totally unique 5/10 album i'll almost certainly hold onto it; i might not feel like listening to it often, but if i ever do that's always what i'll reach for. simply put, it's the best of its kind; the "better" 7/10 album is not.
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And if you don't know, now you know.