No, not at all.
Yes, you could level other classes, play an Alt or whatever you want to define "level everything at 60". Or, you could run the side quests, see the sights, craft, gather, fish, fly, work on your glamours, work on your house, help your Free Company, talk to your friends, make new friends, help newbies, etc...
With this quote;You are effectively defining the game content as MSQ plus dungeons and raids. What about all the other things that you can do in the game? I mean, I'm sorry if you're bored, but just because you don't want to do anything else in the game it doesn't make the game bad or light on content, it simply means you've run out of things that interest you.What do "new players" have in terms of content? The main dungeons they do once or twice to get to 60 and the MSQ.
If the answer for you is not to broaden your interests in the game, then as in any game where there is a finite amount of content (*every* game), once you have done what interests you, you will gradually become bored.