1999: Leave town in a party of multiple players, and venture into an open world to grind mobs, free to set your own pace.
2004: Leave town alone, and venture into an open world to grind quests, free to set your own pace.
2009: Don't ever leave town, line up in a queue to enter a linear closed off instance with multiple players, pace is bottlenecked by controlled daily/weekly experience bonuses.
Your argument here is super skewed. You can "set your own pace" just as much now as you could then. Feel free to level slower by playing less or being bad. Feel free to level faster by playing well, playing more, and / or killing faster etc. You also set your pace by choosing different content. Bonuses are not "bottlenecks." I could just as easily say in FFXI that the pace is bottlenecked by EXP chain breaks.

Noboy's forcing you to stay in town, line up in a queue or enter a linear closed off instance. Nobody's forcing you to group, or do anything. You're just as free to set your pace now as you ever were before. I'd arge you have far more freedom now than you did before as well.

1999: Level up by waiting forever for an EXP party, locating a camping spot and repeatedly killing the same monster(s) over and over for several hours. The only thing that made it at all enjoyable was that you were sharing this long drawn out experience with others.
2004: Level up by repeatedly killing the same monsters by yourself, or by doing quests that award EXP.
2009: Level up by joining a group of people for dungeon runs or guildhests or grinding mobs, by yourself by killing things for the hunting log, by doing quests, by doing levequests, or doing Full Active Time Events.

In 1999 we had 1 key way to level up. That was the only way.
In 2004 we had two key ways to level up.
Today we have many ways to level up