This can be done, but not easily. you have to set up one IFTTT applet for each shortcut you want to use. See the FAQ
FAQ: How to Trigger IFTTT Applets with iOS 12’s New Shortcuts App and Siri
The homebridge option that @sidjohn1 mentioned is much more complex to setup and requires additional hardware, but also gives you full integration. Essentially you spoof your SmartThings devices to HomeKit via a Hue bridge emulation.
Hello, Home HomeKit (and Siri!) control via homebridge
There is also a third party app, Switch Living, which claims to allow easier integration, but to be honest, I’m personally not comfortable with giving a third party of this type that much access to my accounts. But that’s just me.
Meanwhile, Samsung SmartThings staff do not officially monitor this forum (it’s intended for customers helping customers), so the best place to make your suggestion is on the official twitter or Facebook page. 