I think this is likely to be true for every artistic creation that requires lots of capital and widespread human coordination. Ultimately for a TV show to be great many, many things have to go right, and much of what could go wrong happens after the money is spent and the air date is already assured. I'm grateful we've had so many great things, certainly far more than I'll have time to watch in my life. But I'm not a heavy TV viewer.
I think the problem nowadays is that there are so many channels and so much space to fill. TV runs 24/7 now on hundreds of channels. In many cases, it isn't worth the while of a small channel to make an expensive programme as they would lose money.
Sometimes, the "wrong" programme is the hit. I know the History Channel started off with serious documentaries (some of them excellent quality) which not enough people watched. They then tried Nazis and Ancient Egypt, but it seems to be "Ancient Aliens" which is their biggest hit. Its version of history is questionable, to say the least.
TV has a fairly bad record of keeping shows that are already shown to be good alive though because good does not equate profitable for the network or individual decision makers (which are again no the same thing).