My general opinion is that organ donation should be opt-out. Most people aren't organ donors not due to any real objections to the practice but purely because they don't know that they aren't.

Make it easy to opt out for any reason, but also make it easy to opt back in if you change your mind, because bodily autonomy is important in any free nation.

But also people are lazy idiots and for no-brainer medical questions like vaccines and organ donation, they should have to put in a minimum amount of work to continue a bad practice for the wider population. Make the bad practice slightly more work than the good one.