As in games like the old UO and current DarkFall where you level skills etc? I like them as in theory you're always progressing. I think it's cheap of MMOs these days to trick people with grinding for gear rather than levels, it's really the same thing but people hate grinding levels but think nothing about grinding gear.
If there is stuff to do afterwards then I'm all for it don't get me wrong, I play literally every new MMO that comes out but don't feel any have got it right in a long time.
Well this is the thing. UO had no quest line, not much of a tutorial (Occlo / Haven), you had to learn what the commands were (Vendor Buy the Bank Guards some new curtains), the skill grind was generally slow, and the original map was remarkably small - about 20 minutes to ride on horseback coast to coast.
Skill progression (even if it is slow) should be a byproduct of correctly carrying out that given activity, not just an arbitrary "I've killed 80 barbarians today for more skill points, that should be enough to unlock Level 3 Cooking!".
The grind in UO was pretty immense, especially things like Taming, so it took at least 6 months to get 7x GM. This is assuming you had sufficient gold in the first place to train these skills. After that, there was a whole world of trading and adventuring and housing and decorating and guilds and PvP...
I think the reason there hasn't been another UO is that parts of it were horribly designed. Specifically how items were handled, which meant that any item you found could be placed on the floor for all nearby players to see.
Can you imagine 100+ clients trying to render the 3D contents of a noob's backpack strewn across the floor outside of a bank in modern MMOs? Not to mention the artist's time to mesh and texture every item in the game...