1. The skill trees in D2 were awful. If you think about it the abilities were not so great and you really didn't get to try out most of them, let alone use them. Plus you could only reset the tree once per difficulty. If you say the skills are simplified you're wrong... you really have to chose them so they can mix with the stats you chose to have, the fights you're about to have, the passives, etc. You really haven't played much have you?    

2. Whatever... play with friends if you want party customization. Also, after you leave a Public Game the players you played with will be added in your friends list. If you liked playing with them, talk to them. 

3. To be able to use 6 skills is more than enough.  You're not playing WoW.  

4. And the game not being addictive is a bad thing because??