I like to believe most people are in favour of organ donation as it can save lives, and if not donated, organs are useless. The fact is, there are always more people waiting for the organs. When I think about it, maybe many support the idea, but because they never got to sign for it, organs are not automatically used to save or improve other lives.
Then comes the debate whether organ donation should be opt-in or opt-out. I might say it should be opt-out, as I can not comprehend why anyone not want to donate after death, but I know there can be reasons beyond my understanding.
So, the only solution is educating and spreading awareness about organ donation and letting individuals decide what is wrong or right for them.
If you support organ donation, not only signing up for it (if you are in a country where it is opt-in), but also talking about it whenever you can, might make a difference that you might not even realize. I wish the government and educational institutes add it to the curriculum so that people can decide early in their life, but as I can not control that, I will do what I can and hope you do what you can.