Namely soap operas and the like. Its the churning out of old, overused ideas over and over to overwhelm the reader with volume. There is no main theme beyond what ever they come up with this week. While they can be entertaining, I watch sitcoms and wrestling, after a while it is a major waste of time. Or even worse, the writer comes up with one flash of inspiration and just plays it by ear.
Some gifted writers can get away with it, but the majority of it is pure garbage.
Improvision can't be learned and its a talent only a few possess. Second, a thing that really pisses me off is what I call the sidecar. People take a perfectly good series, that mangle it by basically typing out the script again and slipping in a few new elements. An example I particularly disliked was a fanfic pairing Duo and Usagi together. It was staged in the Gundam Wing Univerese and was litterally a repeat of the series.