Too many left wing premises in many of the story lines.
(We've eliminated money and capital punishment, et al)
Too much advocacy for obviously left wing causes.
“We’ve eliminated money and capital punishment, et al”
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That’s pretty much from TNG and beyond, not TOS.
IIRC, money and capital punishment existed in the original series. As for the chronologically later shows, yep - total collectivist foolishness.