2011 iMac as a monitor for m4 Mac Mini

I'm trying to connect my M4 Mac Mini to an older 2011 iMac (running High Sierra) but haven’t had much luck.

I've tried connecting a Thunderbolt 2 cable from the iMac to both a "Thunderbolt 2 to USB-C" adapter and a "Thunderbolt 2 to HDMI" adapter—neither worked. I also used the Command + F2 combo, with no success.

Is the age gap between the mac mini and imac just too big, or is there another solution?