I feel like it can be a mix of both and not dependent on being cosmic, but that's just me.I like them as well, but only at their Silver Age/Knaufs levels.
Here's an example of what I mean: the Mandarin creates some illusions, and the illusions are juuuuust powerful enough to let him get in a cheapshot with his superhuman martial arts abilities while Iron Man doesn't know which Mandarin to dodge. That's so much cooler than if he had overwhelmed Iron Man with Xavier-level psionics, or wrapped the world in a psionic illusion. The rings are cool when they are low-powered tools with just enough OOMPH to COMPLIMENT his personal abilities without rendering his personal abilities SUPERFLUOUS.
In the case of the above, the Mandarin comes across as a next-level version of a ninja, and the rings as next-level versions of a ninja's smoke-bombs and throwing dirt in the other guy's eyes. That's really cool. Mandarin as a Ninja-Lord with a Ninja-Lord's next level tools.
Whereas if you retcon the rings to be cosmic, you destroy all that. The rings no longer compliment his personal abilities, but instead replace them. He ceases to be this brilliant genius schemer with superhuman ninja-lord skills and next level ninja-tools, and becomes this boring Herald of Galactus type. The kind of character who has no scheme, because he is so straight-forwardly powerful that no schemes are needed. Cosmic rings destroys him as a schemer and a martial artist, and it is the fact that he is a schemer and martial artist that makes him interesting.