I hear that attitude a lot in my 'other life'. About how you can't fix the world's problems, etc... I figure that if nothing else, I'm helping the women who come to me to have a better birth and know they have choices. One couple at a time, I've helped over 180 babies have a better birth.
So, even if you aren't changing the world per-se, look at all the people on this forum who, one piggy at a time, have come to realize NOT to buy animals from petstores, NOT to buy supplies where pets are sold, and HOW TO take great care of their piggies so that they are happier and healthier. There is a ripple effect when they talk to their friends, etc - it's all about opening eyes and making people realize there is another way, and that the 'status quo' is NOT what is best for the piggies/animals.
Yes, unfortunately there will probably always be mass breeders and clueless GP owners, but sites like this, and people who work for animal welfare will make those situations less and less and do so much to help GPs, one at at time, by educating their owners on how to better care for them!