You must have missed the current syndicated Star Trek, which has been enhanced with new special effects. However, CBS didn’t go all-out as Lucas did, and most people believe the effects help rather than harm.
I’ve only see “The Immunity Syndrome” (in the UK we’ve only received the cleaned up TOS, not the remastered) a while back, it wasn’t bad to look at, nor was the new theme.
a group of us watching an original series, back in the early '80’s decided we would try singing along. the lyrics were spelled out in one of the many star trek books of the '70s.
we couldn’t get past the second note. we were laughing to hard. the wild leap and the “yond” of beyond had us laughing for hours.
in one the the tos episodes uhura sings the theme song in a scene. she handled the leaps rather well.