If quests are so rare, what is so good about this mud in particular?
Sorry to ask but there are several hacknslash muds around where you play a class and run around fighting monsters either solo or in groups. Usually combat is automatic and often fairly fast and revolves around getting gear together (sometimes covering resitstances and such), then hurling spells or abilities at your opponent until he/she/it drops.
Even among hacknslash muds there are differences. Aardwolf and erion both have pregenerated quests you can do, Aardwolf with rather more emphasis on these and on heavily balanced gear than Erion, Erion with more random collectables, minigames and an imho friendlier community.
Classic six dragons has a light crafting system and wilderness exploration, plus quite interesting combat that is not too fast pased so you can play tactically, also nicely detailed quests.
Alteraeon and cyber assault both have more complex combat with a lot more options than just hurling spells or whacking away until your enemy drops, plus both have serious amounts of quests to do and area to explore which is as much part of the game as the combat (alteraeon also has a major crafting element).
So, what distinguishes Calisty, particularly if there are few to no quests?
With our dreaming and singing, Ceaseless and sorrowless we! The glory about us clinging Of the glorious futures we see,
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)