WoW conditioned players to expect easy, consumable endgame content... especially the later expansions. Players burn through content so fast these days devs can't keep up. Even Blizzard, with all their money, had a hard time keeping up with their playerbase's appetite for more content. If a large company like Blizzard has a hard time adding timely content, imagine how hard it is for smaller ones. I don't get why all these companies decided to mimic WoWs endgame when it's obvious they don't have the manpower to make it work similarly.
Content was slower, and more difficult, back in the day. It was expected to take several months before it was completed, which gave them more time to push out new content. Today, it's not surprising to see people clear new content in weeks.
That said, I don't know if making content crazy difficult again is the answer. The current method isn't working though.
Another thing is the internet has taken a lot of discovery out of MMOs. Content gets data-mined before it's released. Players end up knowing the content before they even play it.
Wildstar has an interesting take on endgame with the dynamic raids angle. If that actually pans out, that might be a new way to approach endgame content.