I don’t see the bullhorn anymore. Not that I ever really used it. But to me its a better way to hook up with other players than awkwardly dropping in on people in TeamSpeak. Maybe I am just socially awkward but I hate doing that and therefore never go on TeamSpeak.
Discord is way more powerful than Teamspeak. This can be both good and bad. So far I have only seen the good. Some servers, Dynamic DCS for example, require it. Not for comms but to manage the campaign generator across clients and the server somehow. I don’t understand it but it seems to work. I also like the web functionality of Discord. On the Blue Flag “gadget” (the live DCS map), chat bubbles from Discord display as people post messages. It helps with differentiating between your own game crashes and server-wide crashes. Discord does also have a WhatsApp-social-media-WeWantToBeYourEverything vibe. It takes seconds to dispense with most of that, but I can completely understand why that would permanently turn people away.