There's nothing unethical about that in the long run since you're still buying music. You're just not buying everything you get a chance to hear. But it's unrealistic to expect that of anyone in an age where you can download 50 albums a day.
Neither band has done anything essential, in their prime or otherwise. But CoF gets the edge for releasing some surprisingly good albums in the last decade. Dimmu not so much.
MA HQ has clearly built a state-of-the-art science lab where they can perform a quantitative analysis to determine which bands are "close enough."
There's probably also an app for that.
While some of these names are abhorrently strange, many aren't exactly bad. They just happened to have been appropriated by bands that cultivate that particular image, logo style, overdone/overhyped sound, etc.
The main problem is that words such as prom, cowboy and Reno are unacceptable choices for metal band names. And Tuesday is the least metal day of the week.