This seems like a problem that's really hard to solve. You basically seem to be in a position where you don't know what Sword and Sorcery is and aren't interested in finding out. Which is fine, but it means your arguments are from a position of ignorance, so you may find them convincing, but obviously others are not going to, and some points are going to be very hard to deal with, because you simply don't have the context to adequately understand them, and it's not context that can be trivially delivered to you.
I'm struggling to think of modern fantasy authors who write stuff that's definitely S&S (or movies, or TV series - Spartacus was kind of close, but without the sorcery - it's sword and sandal, which is a related genre). You have people like Joe Abercrombie who are kind of close, but they tend to lack the mercenary-but-heroic-but-mercenary vibe that S&S typically has. The Malazan series by Steven Erikson isn't tonally a million miles away but is also a kind of extreme epic fantasy, which just sort of slides into being S&S at times. Scott Lynch's Locke Lamora books have a very Fritz Leiber-esque kind of S&S vibe to them, but there's also other stuff going on.
That isn't really true in the tone of the setting, though. Particularly as written by Ed Greenwood himself. Yes, the greatest magical empires might be gone, but most of them sucked pretty bad, and magic is still evolving and modernizing. New things are happening. New societies and cities and nations are emerging, and they're not worse than the past - in many cases they're distinctly better. Overall it is completely fair to compare the FR to mainstream high fantasy. It's no more a story of "decline" than WoW or FFXIV is. Yeah, bigger magic happened in the past (though insanely big stuff happens regularly, like on every edition-change!), but the past isn't "a better time", or even necessarily a bigger one.
Whereas in GH, the past clearly was, in many ways, a better time, where bigger, more important things happened. And this is true tonally, as well as technically.