The real difference is you can watch what you want to watch on demand instead of being limited to their selection of shows on their schedule.
Also, you can sign up for a month, watch a series, then cancel and sign up to some other service. Pay for several services and sure, it's expensive. But one or two? Still a hell of a lot cheaper than Cable ever was.
The fact most content is crap is irrelevant - there's more good content available than any reasonable person has time to watch.