What is so wrong with just not feeling anything for most of your extended family?

I personally don't think what you're feeling is wrong, but it probably isn't helping you either. I think as a family member you are obligated to go to family events and be politely social with your extended family there. You should really make an effort to enjoy these events, and if you can't, at least fake it. I don't think you're obligated to seek out opportunities to get to know them/be with them unless you want to. Sending birthday/holiday cards is nice, I'd suggest it, but again I think you don't really absolutely NEED to. Hope this helps :)