Biggest demoralising factor for me was the matchmaking tool content. The 5-mans, scenarios and LFR weren't engaging at all and were for a long time (in LFR's case still is) the only real way to gear up. It's gotten a lot better, but I'm still having to use these tools on a regular basis; especially if I want to pug raids on an alt.
I can get an alt to 490 in less than a week, then I'm stuck sitting on my ass.
This is the next problem. If I want to do anything fun on an alt, I have to pug Challenge Modes or Raids. All the other content is designed for the lowest common denominator to have no trouble clearing. I don't really get to learn or experience anything from my alts without setting up my own pug or trawling through LFR/Hc Scenarios enough to go join someone else's.
Would be nice if valor points were gone too. They've done a number on how people see the content.
I think a lot of it is just age, though. I wouldn't find my interests so restricted if I wasn't so tired of most of the content.