Why is AirDrop from iPhone 16 Pro Max to iMac Ventura 13.7.4 stuck on 'waiting'?

Without any useful information such as what troubleshooting you have tried it's difficult to assist. So please start by looking over https://it-training.apple.com/tutorials/support/sup115/ to check the basics such as are the devices on the same network, do you have the settings set correctly etc...

Asking an open ended question such as you have on a help forum will get you little assistance as you have not provided us much to go on. Perhaps if you looked over Writing an effective Apple Support Communities Question this will give you some clues on what we need from you in order to be more useful.