Cable TV mission creep
Of the three you mentioned, Lisa, I'd probably have to tip my cap to MTV, which resembles its original format in only the most vestigial sense. I remember growing up in the 80s and having MTV on pretty much non-stop, sometimes watching into the wee hours for one more glimpse of a favorite video. I guess the Internet has pretty much wiped out the viability of a music video network, since you can watch any music video you want at any time. Sadly, they don't seem quite as memorable as the wildly experimental mini-movies we were getting Back In the Day.
Honorable mention goes to SyFy, which is now littered with reality shows and wrestling. I remember when they were going to adapt some of the great classics of sci-fi and fantasy into TV movies and mini-series. Now they scarcely even bother to show science fiction programming, and the movies are cheeseball CGI-fests about giant snakes.
The really unfortunate thing is that it probably wouldn't cost all that much to fulfill their original promise and option some old classics of speculative fiction. I think we'd be willing to put up with shoestring special effects budgets if the acting and script were there. Look at some of the amazing work indy web-based filmmakers are doing with a fraction of what SyFy probably spends on a typical giant snake snoozer...