The future is here but unevenly distributed. So the future was already there, 20+ years ago. Plenty of biz model / programmatic solutions.

I mostly hung out on "The Glass Dragon" (a couple hundred player Diku with lots of added areas) in the very early 90s thru 00s but I also played other muds at that time so my memory might be foggy... Anyway:

A lot of "problems" can be eliminated by simply removing things that are now taken for granted. For example without a real name policy or link to the real world, its very difficult to harass random demographic members. I only grew to personally know a couple players, and even that not very close. Of course I was playing MUDs before the Cantor and Seigel (?) first usenet spam in '92 or whatever it was, so spam wasn't an issue in the early years, but people generally did not share email addresses or other contact info except among their closest friends. In this modern facebook era this is conceptually unthinkable and with socialization comes inevitable harassment followed by inevitable pouting about this unavoidable aspect of the human condition. If you "stole" socialization and real names and the like from a 10's player they'd drown in rivers of their own tears, but there wouldn't be as much trolling either.

Note that an anonymous message board with no reputation has no loss when you troll and get banned, whereas if you invest three hours just to get thru the tutorial zone before you can socialize with anyone, you have three hours invested in not getting banned. So comparing a modern troll rampage to a mud is specious. I don't think twitter would have many users if they forced all new users to go thru a week long 100 tweet training course; of course they would have no trolls.

There are trivial programmatic ways to eliminate theft, if you're willing to torpedo the business model of selling virtual gold on ebay or selling virtual loot or virtual grind as a business model, which again today is unthinkable. The only way to get my loot and gold is to ask me to give it to you. Wiz and immortals did a brisk escrow business as a stated duty of their title/position as ordered by the admins. The often exponential scale of growth of player levels also plays a part, if you go to home point and make a higher level player feel sad, their trash items and trash coinage makes you the richest most powerful lvl 10 you can imagine...

I don't think the extremely class based (as in socioeconomic class) model of most MUDs would be socially tolerated today, but back then there were plenty of higher class immorts and wiz and the like who would, um, not exactly spare the rod to spoil the child. They were not jerks, if they were then the mud would be empty, but they had no financial qualms against doing everything up to and including banning your IP range. This is utterly unthinkable in the modern era where trollers feel they purchased the right to be jerks by paying their monthly subscription and bought their virtual gold, and every disciplinary action therefore carries a financial penalty that has be to (stereotypically poorly) balanced against the offense and subsequent financial losses the troller causes to the rest of the community.

Now for a nice controversial opinion, I believe most (all?) modern designers intentionally design MMORPG type games to encourage a low dull roar of drama we claim to hate, because there exists a tiny, profitable, subset of players who expect it and find it vaguely enjoyable as long as it doesn't happen to them etc. Social engineering does not inevitably lead to a utopia or hell, much like in the "real world" the most profitable/popular for the important people involves most people muddling thru some filth.