And to be clear, I'm not trying to knock Hubitat. It is a great system, and it is my primary home automation hub. The other systems I mentioned have plenty of issues/cons of their own.
The point of all that above is that MQTT is a vendor agnostic, open protocol/system way of sharing data between platforms. No goofy APIs needed, no licensing fees, no worry about "will it work in XYZ system". Once you can get the data from a platform into MQTT, you can use the data and devices wherever YOU want - not just where the vendor decides.
