I've a QR app because I need advanced options, but just tested that my stock camera app when presented a barcode or a QR read them without any action. It offers to open the link in the browser, to connect to the wifi or to search the numbers of the barcode.

My guests doesn't ask for the WiFi pass, they see the QR hanging and ask "what is this QR for?", "It connects to my WiFi", and they immediately try it (succesfully) out of curiosity, "It's cool, how is it done?". The don't understand the magic behind, but don't need a guide to use it.

Android phones might all do this now for all I know, I have no idea. My phone is a few years old so hard to say.