The thing about the skills in D2 was that at the time the game came out, it was a completely new and unique approach to character building. The D2 skill tree was poorly designed and balanced by modern standards (although it was improved by patches), but by the standards of the time it was pretty amazing.

I also find it interesting to remember how in D2 when a new patch came out, it would frequently completely destroy someone's character build that they had spent 100s of hours working on, and because there were no respecs, there was nothing they could do but start over. I don't think people would put up with that today.