In the long run, the new "Eras" filter will do what you are familiar and comfortable doing.
The mistake ebay made is they deleted the Golden Age category from thousands of listings. They could have easily just assigned those same listings to the Golden Age Era. But, instead they left Era blank. As a result, thousands of GA comics are now part of the drek.
To fix it, sellers will need to update all their listings to include Golden Age, or Silver Age or whatever with the correct Era. If you have hundreds, or thousands of items listed, have fun with that. And, until all those thousands of listings are updated with the Era, they will be continue to be lumped in with the drek.