Kaodi
Legend
I think you've made an error in this comment. You're focussing on just WotC published settings. In fact, 3E was the Dawn of More Settings Than We've Ever Seen Before.
There have always been tons of settings. Just most of them were not published.
In any case, even assuming that 5e is OGL (and there are reasons to believe it will not be), it is a mistake to think that most 3pp have the sort of cache that an official D&D setting does. Even the good ones do not tend to get mentioned anywhere near as much as the official D&D campaigns - partly perhaps because D&D worlds often also have novels, games, and other material backing them up.