While we're speaking about anachronism, do you realize D&D is full of that ?
Mindflayers, Beholders, Neogi, Grells, are creatures with a strong pulp sci-fi feel.
The displacer beast's look is copied on Van Vogt's Couerl. The Xill is copied on the Ixtl from the same author.
Is there a need to mention the UFO from, IIRC, In Search of the Unknow ? And the technomagical ruins of Blackmoor ?
Iron Golems have often be depicted more like robots than like animated armors or statues. There also is a large number of clockwork creatures, not all of them coming from SpellJammer.
And of course, there are psionics
D&D is not medieval Europe. It don't looks like, and it requires work to be made in the semblance of it. So, why would people look like medieval Europeans ? Especially adventurers, who are frequently flashy guys and gals.
As long as they don't look like comicbook superheroes, I'm fine with it.