I have also found this to be the case. I can easily sit down and read something enjoyable for hours on end, but I try to watch a movie and within 20 minutes I'm wishing I was anywhere else. TV shows inhabit a kind of middle ground between the two, they're still tolerable but I find myself enjoying them less over time.
I can't say I really regret this change, I haven't noticed any real downsides. There's too much content and not enough time these days.