Not only can you move while striking, but distance management is really key. In UFC 2, it was basically impossible to use a short armed fighter. But in UFC 3, if you are using a longer reach guy, you have to manage distance to land your shots at the end of your strikes or you wont bring as much power to the shot. And conversely, the short armed fighter is much more dangerous inside. Combine that with the ability to strike and move, slip strikes while moving, and suddenly its much more viable to use a shorter fighter against anyone. I remember facing Barbosa while using Alvarez. My strategy was simple, get inside on Barbosa. Crowd him so his kicks were less effective, and my strikes were more powerful. I was able to do this beautifully. By the 2nd round, I had him broken down.