I get what you guys are saying. I think that we're just talking at two different levels.
The reason that I say that the UI isn't the issue is not because I don't recognize the value of dropdowns in a choice list being hella faster than typing it out after looking through a help file.
I just think that, even with UI changes in a client (whether app or web), players face much larger hurdles than just the command structures. You will see a fundamental shift in how MUSH is played, period, if you (as @Arkandel proposes in his example) remove the physical movement from room to room on grids. You will start seeing people hiding/ignoring information that is, in today's MUSH standards, designed to be read, followed and dealt with in an IC way. That's just one example, and I don't think that I'm being old-dinosaur by pointing this out.
Shift every rule, check and validation into a web client, and you will have a complex web client. Why? CharGen is complex. Shift every +command into a web client, and you will get a complex web client. A window for seeing who's in the room, who's online, including filtering for "Everyone in WHO", "My friends", "Just in this Room", or "My Faction". That alone speaks to things being complex to learn, potentially lending to people missing things.
Imagine +watch now being desktop notifications (and yes, people would ask for it). Imagine the web client interface for managing that functionality. Pages and channels, too, in their own windows if you like, but do we now do Slack-like @-mention notifications? What about +beep/+alert?
Sit back and try prototyping out functionality of a MUSH into a web client. That is a good first step to having this conversation, in my opinion as an engineer. Let's start going through actual UI/UX exercises and proposals.
I get that you propose and think that it will somehow lower barriers of complexity in entering players' experience. I get it. I just don't think that it is as easily solvable as you think. And, if it is, I am not yet there with your vision, and I think that I (and others) need to see what you envision. I'm happy to help in this project, as I said before. Promise. EDIT: I'm already deep into working on it here.
But during the envisioning phase of any project, we need to all agree on goals. In this case, that is a concrete UI/UX.