You can think of Hiddify as an aggregator. It is simply a frontend to manage the underlying protocols with ease without delving into too much technical steps.
When it comes to China and Iran at least, protocols keep getting patched very fast, and new protocols keep getting developed at an exponential rate, so Hiddify creates VPN configs for all of the available protocols at that time, allowing the user to switch between various configs with ease.
Indeed, this method proves to be useful as many users are able to bypass restrictions, and avoid DPI.