I personally don't think being otaku is wasteful. If you enjoy it then go for it as long you are not bothering other people who may not share your interest. I watch anime, play games, read mangas, bought anime posters and figures. Best of all, I have met other people that I otherwise would not have in contact if it weren't for anime/otaku.
Although I would hope that you will go out a little and enjoy outside rather than stay locked up in your room all the time. ^_^;
Also, don't forget to discipline yourself to get a career that will finance your interest too.