Actually, it is the only (display) protocol. HMDI Alt Mode, while specified, never really manifested and is effectively dead. DisplayPort is the only alternative and is more flexible anyway.

Its packet-based nature is not relevant for DisplayPort Alt Mode, by the way, because it gets dedicated pins. Sometimes enough for two lanes, sometimes enough for four. It's hilariously consumer-unfriendly. Only Thunderbolt leverages the packet stuff and can transport up to eight lanes worth of DisplayPort.

macOS does not support MST.

Who is supposed to get this? I don't know.