try alter aeon if you haven't. It was my first ever MUD, so i think it's pritty easy to get in to there as well.

Agreed on Alteraeon, however two others that I can highly  for first time players are erion and Frandom.
Frandom has a very interesting and unique tutorial system, yet one which lets you get straight into the game with learning just a few commands, whilst Erion has a fantastic mud school and lots of easy to do player missions that set you to some of the easier areas of the game.

Aardwolf has a similar mud school, but the game itself gets harder and the community are  friendly than those in Erion, plus in Erion useful items are easier to get.

I'd also say four dimensions, since then basically the mud school takes you to your firs remort, however the big problem there is what the hell you do after you finish mud school.

Generally this is the problem I find, not how good a given mud's tutorials and newbie areas are, but how easy it is to go from the hand holding tutorial stage, to actually finding stuff to do in the main game, since some games like avalon and diskworld make that transition so jarring suddenly you go from being lead from place to place to literally wandering around with nothing to do.

Erion has the same system Aardwolf does for running to things, but imho erion is more logically layed out and smaller and a lot of the goals are less obscure I still need to retry materiamagica, I had major issues with it at one stage though  know its been heavily reworked since then, ditto with avalon.