Meh, hairsplitting. The second you leave whatever setting you started in, you're stuck in Planescape/Multiverse (because the two are inseparable). Every module, every guide baselines to the same thing. You have Asmodeus ruling Hell, you have Demogorgon rooting around in the Abyss with Orcus as the Demon Prince of Undead. So on and so forth.
Never minding that in a number of settings, it makes absolutely no sense for these things to even exist. Why would Krynn need a Hell? Why would my Viking setting need an Abyss? But, as soon as we cast Plane Shift, poof, instant Planescape.
Not so much miserable as very disappointed. I haven't bought anything planar for D&D in twenty years or so. Because I know it's just warmed over Planescape. No setting is allowed to have a unique cosmology regardless of how much they try, because, again, it all has to be connected to the Great Wheel and all those extra bits and bobs that go with the Great Wheel and Planescape. So, we can talk about The Gray, or whatever it is that makes Eberron cosmology different, but, at the end of the day, one Plane Shift spell later and we're right back in the middle of Planescape.
Yet, despite that, not a single setting or module EVER actually allows you to break away from the Planescape Great Wheel. Every module, every supplement, right into 5e with Mordenkainen's, we're right back to Blood Wars and Demon Princes. Whoopee. 4e tried to revamp the planes, and got crucified for it. To the point where the 4e cosmology and planar elements have been entirely (or mostly entirely) excised from the game in 5e.
Like I said, we're not allowed to have anything but the same warmed over 2e Planescape garbage that has been forced on the game for twenty or thirty years. Nothing else is acceptable.