Twitch, basically means you have to aim, and time skills, like in a 3rd person/first person shooter.
The alternative being turn based, like FF series, or Traditional tab fix'd target mmo. Where you click and a person and hit and miss's are decided witha dice roll instead of actually aiming.
People believe that the turnbased style, reduces the amount of skill ingame, this is because everything is controlled by dice rolls, which can usually either be increased by talent trees/gear/skills trained/weapons/other factors that are simply grinded for.
This often ends up making the game balanced to "who ever grinds the most, WINS!".
Twitch is the opposite, or rather, SHOULD be the opposite, requiring the player to manually aim, and critical dmg/hitbots dmg, dodging blows, is down the the players reaction time and his positioning. The problem with Twitch Pvp, its affected heavily, by things such as lag, and cheats. Such as aimbots/speedhacks. What people in this game are mainly complaining about is the Lag. As it makes it impossible to hit someone with good timing, dodging hits with timing etc. And often ends up as a button mash fest.

The Solution? Clever, and Innovative Programming. Who has the Solution? Bill Gates. But he keeps it for personal use only.