It's a game...seriously. ???
If you're not getting what YOU want out of it, then you quit. It's that simple. There is nothing forcing you to stay...nothing makes you spend your free time in raids that you don't like/enjoy anyway.
Burnout happens...a lot for raiders. Even when the game was "perfect" in the eyes of most hardcore raiders, people still burned out and quit. I did...twice. There is nothing wrong with taking a break. And if taking a "break" turns into quitting forever...so be it.