That's not true, there's a lot of soft produce that you can juice (papaya, mango, etc). When it comes to fruit, you can't juice the things that don't contain a lot of water (banana, figs, etc). Start reading some juicing books and you'll find out what you can use.

Go to http://freedomyou.com to learn the basics and specifics of juicing. There is a lot of free info as well as some great ebooks at reasonable prices.