One of the big differences I touched on in my first post is some feats that you needed to get your character concept to work in 3e, are just not needed in 5e. In 3e if I wanted to dual wield I needed to take a feat or two to make it effective, in 5e I just pick up two short swords no matter my class and go to town. In 3e if I wanted to be an archer the firing into melee penalty of -4 was so big why bother without having the right feats, in 5e if the DM rules the target gets some cover it is only a +2 to their AC and if I am a fighter or ranger archer my fighting style overcomes that easy enough, and if not I don't feel like I need the sharp shooter feet where in 3e taking precise shot for any archer was almost mandatory, and that meant also taking point blank shot first.
The simpler ruleset of 5e, and the fact that you can do things like just pick up a two short swords, use your dex to hit and damage and get a second attack at no penalty to hit on either attack is so nice. The feat taxes of 3e are gone, and that to me is huge.