I like playing against others, even though I have a losing record in RS it's a fun experience (for the most part). What I don't like is everything else that comes with it.
First, it takes too much focus away from other aspects of the game, and also forces the devs to consider monetization when creating features.
Secondly, it requires the players to either 1) grind A LOT or 2) spend money to constantly and consistently keep up with other players as far as your card collecting goes.
Thirdly (is that a word?) it tends to foster a toxic environment where people are quick to lash out on others.
I will admit it accomplishes it's goals, that is to bring in post release money.