I find, in many ways, that TOS has aged better than TNG. TNG seems to scream 1980s to me.
And TOS doesn't scream 1960s?
To me it screams 'Star Trek'. Despite the beehives and mini-skirts, it shares nothing with Twilight Zone, The Nanny and the Professor, The Big Valley (or other westerns), Rat Patrol, and doesn't particularly look like The Time Tunnel, Avengers, Lost in Space or Voyage to the Bottom of the Sea.
It looks like Star Trek.