DoD is not setting agnostic, the modules that inspired it are, but DoD is based in the forgotten realms, DoD is Forgotten Realms canon, and in fact DoD largely caused the reshaping of the Eastern Part of the Realms. Old Empires Source book was written because of DoD and between the two books there were massive implications for the Eastern half of Faerun. Mulhorand, Unther, ect... Were massively altered because of DoD from Ed Greenwood's vague idea of these places and fleshed out. There are references to Mulhorand, Imaskar, Durpar, and more. It was the first adventure in FR and I think it was the second FR book published after a novel. It has huge setting importance to FR.
Whoa, calm down there FR fanboy.
The original modules in the series I3, I4, & I5 very clearly tell you right on the covers that they
are the Desert of Desolation series.
And I quote:
"The 1st module in the Desert Of Desolation series."
"The second module in the Desert Of Desolation series."
"The last module in the Desert Of Desolation series."
If you'd like pictures, Google it.
So one can very well talk about the DoD as being setting agnostic & be correct. DoD is the name of the module series, Pharaoh/Oasis of the white Palm/Lost Tomb of Martek are actually the chapter names/subtitles.
DoD existed before your precious FR.
BTW, you want to know what other wildly popular module is setting agnostic?
...
wait for it...
...
Ravenloft. Y
ep, good old I6. Also written by Hickman.
Though I suppose the case
could be made that it actually exists in whatever world the original I3-I5 does as on p.28 of I5, in Marteks treasury, on the Nonmagical scrolls table result #2 is: a poster:
Visit beautiful Barovia 
Me? I always read that (even as a teen) as a bit of cheeky marketing/humor by Hickman, not actual world building.