It's death Jim...
Not just a loss of our generations childhood past but of the way the future was. An optimistic primary coloured, good natured one.
Four more centuries to go to get back to 1966.
Most of all though, Star Trek was a celebration of friendship, good fellowship and tolerance; a spirit that makes it's mythology so beloved and part of the collective baby-boomer psyche. That, and the flawed and warm charisma of the stars. Even their kitsch and ludicrous musical styling's and other eccentric personal endeavours are/were charming. All of it life, affirming, positive; harmless. The stuff of love and gentleness, joy and smiles. The past is another country, the future another universe. the spirit of (the) enterprise the quest for modernity and hope is what will transport us beyond what we are to what we could be. As for now we have worse that Klingons within and are light years away from being acceptable to the United Federation Of Planets. We still have time though. We must not lose our way and should always endeavour to go boldly.