Whenever someone needs life saving measures on the field like Hamlin did, obviously the game should not go on. Seeing a teammate or opposing player die on the field is not what these players signed up for.
Now, here’s where I am going to sound insensitive.
When it is a spinal or head injury, players are very aware that these are much more common and they all have accepted that as a possible fate of their playing football. The game should go on in those cases.
Pre-season? Don’t care if they cancel those games with nobody being hurt.