There seem to be a lot of problems with this argument, at least as presented in the blurb (TFA is blocked at work.)
First, the amount of time spent watching stuff is a poor metric by itself. What you really want to know is the amount of enjoyment people get out of the service. Admittedly that is very hard to measure accurately, which is why they want to use "hours spent watching" as a more easily determinable value. However they shouldn't forget that the map is not the territory.
As long as people are subscribed to the service they're going to feel compelled to get something out of it. It's the old complaint of "a hundred channels and nothing is on", and yet people kept watching, at least until something better came along. For a lot of people if they have Netflix and they feel like watching a movie they're going to browse around until they find _something_.
And there's a strong corollary, if people feel like they _aren't_ getting their money's worth out, they're probably inclined to cancel the service. Which means suddenly they're not being measured in your survey anymore.
Of course what's being measured here is the balance between movies and TV, which _might_ not be affected by people deciding there aren't enough good movies on. However the above would still hold true if their (non-original) TV content had also seen a similar decline. I know a couple shows i used to watch have disappeared off of Netflix. Are there actually any statistics about the number/quality of TV shows they've had available over time?
Finally, saying that "a majority of fans" have already seen blockbuster movies is just dumb. Of course the "fans" who were "passionate" about the movie have already seen it. They're probably also the people who are going to buy it on DVD or BluRay. They are not your customers in this particular instance. The people who are waiting until the movie is on Netflix/Cable/broadcast TV are the people who said "that sounds kind of cool" but never got around to watching it before it left theatres. Given that they weren't gung-ho about it in the first place they're probably not going to want to rush out and buy the DVD sight-unseen, they're just going to wait until they can rent it or catch it on something they have a subscription for. There may be no one particular blockbuster movie that audience especially cares about, but if your service doesn't carry _any_ of the blockbusters then i expect that that's a serious mark against it in the eyes of many consumers.