Unbelievable that they stuck with that design for this long. It was even worse before unknown caller filtering was introduced: I would literally be DDoS'd from my phone multiple times a day from random numbers, iirc with no option to decline if your phone was already unlocked (i.e. using it when it a call came through)!!!
Took them a pandemic worth of phone usage to realize how irritating this was. When lockdown/WFH started, my company was using Google Meet, and everytime there is an incoming call it used to go full screen completely blocking for whatever purpose I was using the phone (or what ever I was hearing or saying). Though Zoom integrates with Call feature (not sure what's the technical term for it), whenever there is an incoming call between a zoom call it used to go in waiting.