I'm 29yo ICT engineer student from Finland and I host Mumble for my friends on my private server. English is not my native language. That in mind.. here goes:
In my humble opinion, Mumble needs to evolve. Not just by improving the code, making it faster, adding features, but evolvement as a whole project.
One of the core problems of Mumble is that it's designed/made by nerds, for other nerds. By nerd, I mean a person who more or less knows how to use a computer properly.
Most of my classmates (ICT engineer students) don't know how to use computer properly. They know how to use photoshop, or how to write a program, or how to design & install & maintain a network. But they don't know how to choose parts for a computer, or how to build a computer, or how to install an OS (any OS) or how to use that OS properly. They know what they have been taught, and nowadays it's limited to the field they are studying. Everything else is irrelevan since it's made too easy. Computer doesn't work if it has no internet. That's what they know. And no student (with an exception of the telecommunication students) can fix the problem of non-working internet connection.
Additionally, they can't use Mumble, at least not without guidance.
I've invited all my gamer classmates to Mumble and they did join but not without problems. All of them had one or more issues, about how to get it working properly. Mostly the issues were simple, like how to get into the server or how to properly setup the microphone settings. All of them said it's quite hard to start using Mumble. I agree with them. Later on, they said that Mumble is ok. They got used to it, so all was good. Then came Discord and all the classmates of my Uni switched to that instantly. They said they switched because it's just so much easier. And again, I agree with them. Personally I don't like Discord and I will never use it.
But the problem is there. Mumble is too hard to use. People who aren't so tech-savvy, will never use mumble, or if they are using it, they tend to get away from it and they will leave, when a chance is given. Discord is suuupeerrrr easy when compared to Mumble. Also it looks nicer and is generally more social-looking than Mumble.
I've made it as simple as possible for my users: they can use just one small info to join my server: "akq.fi" - that's the address, with default port, and no password - "just download and install Mumble and come akq.fi !" I say. But it's not enough. It's still way too hard.
Personally, I love Mumble. It's super effective, lightweight, fast, efficient, minimalistic and just works very well. But I am a nerd. For me, this stuff is easy and I love it. But my friends - the users of my Mumble - don't really care for Mumble as a software. They just want something that works.
My dad used to know everything about cars: how they work, how they are built, how to fix them and so on and so forth - I have no clue or interest about cars. To me, they are just tools: all that matters to me is to get from point A to point B. Just like my friends want from VoIP-software, or a computer. Back in 90's, when 5% of the people had a computer, 95% of those knew how to use them properly. Now that 95% of the people has a computer, 5% of those knows how to use them properly. Cars have evolved to a point where knowledge of how the cars work is not needed anymore. All you need to do is drive, and soon, even that is not needed, you just need to know the location where you want to go.
Also Mumble needs to evolve in similar way. Otherwise, Mumble will wither and die.
Or that's how I think it will go. It's an amazing software that I love and keep loving until it's not usable anymore - like IRC

How much does the greatness of a software count, when the targeted users can't or wont use it?
What can be done? Well, as a nerd, I don't know much. But I think Discord has done something right. Maybe copying some ideas from it would help? Mumble-server usable through a web-page, without client-software?