The ratings, the plots, the characters, the actors (with the notable exception of Billingsley, who owned them all), the music, the lack of expositionary cohesion, the contrived situations, the squeaky-clean endings, the oh my god we're so multi-cultural ethnobolllocks stereotyping that all American shows seem to do these days, the messing with the timeline before they even started time travelling, the need to try and crow-bar in the popular icons from the other series (Khan, Borg, etc) just to lift up one episode... I could probably go on.