I suspect it would be a lot more popular if people didn't risk getting dragged into a courtroom for doing it.
> freely allowing remixing will only increase the ratio of junk vs good art.
Remixing has the ability to take bad art and make it better. Most of everything is garbage, but fortunately nobody is forced to be exposed to it all either. People who don't want to spend their time looking outside of narrowly curated selections of available content or what's already gained popularity never have to. All art is built off of previous works, and even if someone creates a work that you hate, someone else may by inspired by that work to make something you love. It doesn't make sense to want to prevent the creation of new creative works out of fear that they might not be "good" in your opinion.
Even if, somehow, it did make sense to hinder the creation of new creative works copyright would not be the tool for the job. Copyright already has a job. Copyright is supposed to encourage the creation of new creative works. Sadly it is currently being used to suppress art and artists, which is why it is broken and needs to be reformed.
There are some people who want copyright to be as restrictive as possible. Very wealthy and powerful industries for example. They've spent a lot of time and money to try to convince us that copyright should be as restrictive and long lasting as possible, but that's entirely for their benefit and not ours. It's bad for art, it's bad for artists, and it's bad for the public as a whole. They've convinced us to muzzle each other and lock up our own culture so they can increase their profits. The longer it takes us to fix that, the more great art we lose.