I'm sure the donator ranking was created when Bitcoin was worth a lot less than it is now. 10 Bitcoins is a lot.
True. But you're not saying that it should be decreased now are you? I don't think it should. Having a lower rank (e.g Supporter) would be fine though.
I wish I had enough to donate.
You can always donate smaller amount if you want. However you won't get the donator rank.