This is all a difficult communication problem, but it's doubly difficult because decisions need to propagate up and down your communication hierarchy in seconds. Being able to manage this level of communication without it being a hopeless clusterfuck is a defining feature of effective organizations of players.
In fights with 20-50 on each side particularly, it's really something to have the "pulse of the fight" because as a healer you can tell how well that's going.
A mumble server can be hosted with fairly low requirements if you're an org with less than 50 members in voice comms, and it's pretty embarrassing that a seemingly large majority of corporations can't even get 5 people into a call without an act of congress when gamers have tools like this so well explored.
If it's not available on, say, Discord, why is that? Do people just somehow make do without it? Or is there some other compensating feature?
Discord only allows you to be a membere of one channel at a time.
It is not an uncommon set-up for fleets to have the important people have their own channel talking about secret stuff and another one for the rest of the fleet.
Then the ones from the secret channel have two buttons set up, one to talk just to them and one to talk with the entire fleet.
So, while the feature is a must-have for a small subset of users, it's probably not seen as being worth the trouble when just supporting several flat channels is more than enough for the 99% of Discord's potential user base.
I'd still hope they at least add some kind of "broadcast to several channels" option, since that seems like the simplest version that would still be useful, but I don't really expect it.
I'm going to need a number crunch on that.
More seriously, my point was not (heaven help me) that Eve players are disorganized but that 'massive raid requiring structured multi-party voice comms' is not a common problem gamers in the current market find themselves needing to solve.