The general public don't care about Star Trek, or sci-fi in general, much and that's been the case since the original series was abruptly cancelled before it even finished its 5 year mission. Is TOS crap because it got cancelled?
Science-fiction and fantasy films usually do pretty well at the box office.
Honestly, TOS ran longer than it probably should have based on the time-period in which it was produced. Whether it's the 60's, 80's, 90's or the 21st century, you have to produce material people want to watch. Trek didn't evolve with the rest of the TV/movie business, which is why it fell on its collective ass in the early 21st century.