The Aqara devices don’t work with Hubitat either. Xioami only intended them to work with their own gateway, and they are, as engineers say, somewhat “idiosyncratic.“ So you can’t really blame smartthings for that one.
Just as one example, they don’t work well with most certified zigbee Home Automation repeaters. That can be a real problem and it may be that when you rebuild your network they chose a different repeater than they had previously been using.
The IKEA Tradfri bulbs and plug in switch do seem to have better luck repeating Xioami messages, so you could try some of those. There are some Hubitat customers who added a second hub just to run a network of xioami devices and IKEA Tradfri.
You can talk to people using the Xioami devices with SmartThings in the following thread: