I actually think 5e has its own setting. Kind of. It’s just an extremely broad meta-setting, in which all the various D&D (and some MTG) worlds are subsettings within. WotC calls it “the multiverse,” and many fans have observed that its metaphysics and cosmological rules are kind of a hybrid of Planescape and Spelljammer. But over the course of 5e’s lifecycle, some unique details of this setting have emerged. The idea of the First World is the most obvious of these, but there’s also, like, the origin story behind the Deck of Many Things with Asteria and Euryale. The whole Radiant Citadel, etc.