The original release of World of Warcraft had a limit of a few thousand per server too. It's only much later that this got increased. In the classic MMO era there's really only EVE Online that pushed to 10k and beyond, and never in the same star system. Single star system was limited to around 500 people for the game to still be playable. It's only later that they added time dilation which allowed for thousands to be in a single system at once.
The original release of World of Warcraft had a limit of a few thousand per server too. It's only much later that this got increased. In the classic MMO era there's really only EVE Online that pushed to 10k and beyond, and never in the same star system. Single star system was limited to around 500 people for the game to still be playable. It's only later that they added time dilation which allowed for thousands to be in a single system at once.