I can see that, but plate armor was prominent in the later middle ages too, pre-Renaissance. And D&D has no gunpowder weapons, which were starting to be common in the Renaissance.

Then again a lot of "medieval" movies/TV/games mix Renaissance stuff in.

the DMG has Pistols & Muskets, and there's also Laser Rifles in at least Rime of the Frostmaiden. They just tend to not get used cause they don't really fit in the rest of the setting.