I would like to add a term to the mix: micro-setting. The idea is that so-called micro-settings work equally well or better as something to add to your default setting--be it homebrew or a standard D&D setting like Golarion or FR--but may have limitations as a setting you come back to, again and again. I would argue that "high concept" settings like Ravnica, Dark Sun, and even Planescape (especially Sigil) are more frequently used as micro-settings than as default/home settings.
This is not to say that one cannot use them as default settings. But I think the micro-setting usage preserves their uniqueness and exoticism. It is similar to the idea that in most epic fantasies, the protagonists starts in a relatively mundane and relatable land: the Shire, for instance, or Two Rivers, Gont, etc. Then the voyage into Unknown Lands happens; the further from home you go, the more different, exotic, and dangerous the land becomes. To some degree Euro-centricism is at play, but mostly because D&D originated in the West, primarily based upon European tropes.
The Dalelands, and most of the FR, is close enough to home, and to familiar tropes, that it is easy to get a sense of it. Planescape, Dark Sun, Ravnica, Spelljammer, etc, are different, exotic, less relatable. If you make them too relatable, it may take some of the charm away.
Again, the point is not that they can't be used extensively, but that I'm guessing that most D&D players use a more standard setting as their default, whether within a single long campaign or over the course of their careers, and may venture out to Sigil or Athas, but them come "home," rather than using Athas as home and foraying to Faerun or the Flanaess.
Yes, everyone is different, and I'm sure that some here use those exotic micro-systems in a more "macro" or default way, but I would guess that this idea holds as a general trend. Micro-systems are also often used as inspiration for home/default settings, as thought-pieces. One of my favorite non-D&D settings is Talislanta, which I've only game in a couple times but always loved for its creativity (I mean, the author came up with it under the influence of psilocybin, I believe).