No goal is meaningless.

All goals which do not provide a strict in-game benefit are logically speaking completely meaningless, and do not provide a sense of satisfaction a typical MMORPG player would get that would make them want to do such an activity.

Typically most of us normal humans want some sort of a logical goal or objective to pursue; not meaningless grinding to achieve 99 stats, which provides no strict in-game benefits. Or a task to pursue after you have acquired 99 stats, if there is an actual in-game benefit for doing so.

These goal become non-existant once you cap your stats and get max gear. There's no further goals to pursue, even though there's still plenty of room to fill between the level cap of 99 and 76. So it seems like OSRS is not populated by many motivated, goal-oriented MMORPG players.

You get xp, ranks, a permanent spot on the high scores if you get 200m xp, and a sense of accomplishment.

• XP is completely meaningless once you reach 99. It's just a number. MMORPG progression ends once you reach level 99 and get max gear.
• A spot on the high scores is completely meaningless since it doesn't grant you a reward. Most players don't find grinding, gaining large amounts of EXP and comparing their process to others, enjoyable. No, most MMORPG players want good goals to pursue, to give them a strong motivation to grind out those goals.
• A sense of accomplishment in normal humans is typically linked to a good reward. Getting 200m isn't a "reward" since it doesn't provide any in-game benefits. A counter-example to that would be conquering a powerful boss, which drops some sort of an item reward, that is useful for your character or an activity that you are interested in doing. Thus, getting 200m for no reward goes against the basic principles of MMORPG, which is to giev you some sort of a reward to give you a strong motivation for pursuing it. Most players seem to not want rewards, so it seems like they are not MMORPG players.