Use macros, grind ore, sell bulk, buy the world~
But at the end of the day even if you bot etc. Who cares, all you're doing is increasing numbers on the screen. There no genuine fun in that.
When it comes to RPGs for me what is fun is exploring the world, figuring out the storyline, solving the quests/puzzles/problems/challenges.
In an RPG there is only a limited amount of these things, so once I've done all of this, it's sort of pointless doing it again, because I already know the storyline or how to solve the problems,etc.
In an MMORPG, same kind of thing except with other players as well. I think in MMORPGs what keeps them genuinely fun in the long term after doing lots of the singleplayer-RPG type stuff, is the political aspect of the game, and other interactions with other players.
In runescape I found very little of this, or not enough to keep me interested, the only thing that seemed to keep people interested in the long term was the grind, but I think this is very dangerous, as it psychologically tricks you into spending tons of your time doing something which firstly is actually dead boring, and secondly is not actually useful, since it's just a game, your not actually making money, etc in real life, which would actually be useful.