I think the author overstates the premise. Yes, there is a tendency for "bad" art to get forgotten and "good" art to be remembered. However, it's not so strong of a tendency that it's wise to rely on it. Plenty of terrible music has survived the ages, and I'd be stunned if at least as much excellent music hasn't been lost to time.

The "darwinian" thesis confuses quality with popularity. Just because something is very popular doesn't mean it's good, and just because something isn't popular doesn't mean it's bad. There is a correlation -- something good is more likely to become popular than not -- but it is a weak one.

Part of the problem is that whether or not a piece of art is good is very subjective. I don't think it's really possible to say objectively whether or not any given piece of art is good or bad. You can only say if you like it or not.

I prefer to talk about art as "successful" and "unsuccessful". If a piece of art makes me feel something the artist intended for me to feel, it was successful, otherwise it was not. That, too, is subjective of course: what resonates with me may not resonate with you. But at least it isn't trying to characterize the aesthetics itself.