As a TOS fan, I disagree with that. TOS might have had dated drapery, but it also had some flagrantly progressive elements, arguably more than many of the series that followed it. It’s just that the world has moved on, and many of those progressive things are either the norm, or seen as regressive, like the Miniskirts, Uhura being part of the bridge crew, or having an American, Russian, and Japanese man serve as part of the same crew, at the height of the Cold War.
Part of it might also be that they didn’t see Trek as anything more than “cool space show, with a whole bunch of scantily clad men and women”, and didn’t bother to look any deeper, not unlike Star Wars. It’s just guns, cool ships, and shooting, with the imperialistic allegory being ignored, or gone unnoticed.