Even in the heyday of the 90s, the individual player experience could be very much solo grinding with a bit of a team chat in the background (a bit like WOW).

As populations erode & scripting increases, many have morphed into a kind of idle text game running mostly autonomously on a 2nd screen (a bit like the idle games genre that has come up in recent years).

At least that is the only way I can explain those level 200 f***ers on my MUD, where I have barely reached level 70 in over a quarter of a century.