OSRS exists in a pretty fascinating place, mechanically.
High level PVP play is basically a turn-based-tactics game, with some moves (attacks or spells) taking more "ticks" than others, meaning there's a lot of bluffing and mind games in anticipating what your opponent will do next.
If you're really fast, you can even equip tank gear for your opponent's attack, then swap back to mage gear for your own. Very strong if you can pull it off consistently due to how paper thin mage robes are. Not sure how many other games are that...slow?
And yeah, a lot of people are quite predictable and easy to read. In fairness there are only a handful of things you could possibly do in a fight :-)
High level PVP play is basically a turn-based-tactics game, with some moves (attacks or spells) taking more "ticks" than others, meaning there's a lot of bluffing and mind games in anticipating what your opponent will do next.