If you boil ribs the terrorists win. Just cook them for a long time at a low temperature (225 – 250F in the oven/grill) and they will be very tender. When you cook beef slowly and to a very high temperature (~185-195F internal temp), even tough cuts of meat, the fat (even 90& of the “gristle” will render and become like jelly. You must do it at a slow rate and low temperature or otherwise the muscle fiber will contract and squeeze all the fat/moisture out leaving a dry piece of meat. But if you do it slowly and for a long time the fat will render creating a tender piece of meat.