I am a humanitarian aid worker working in emergencies with a decade under my belt. I am not saying civilians are not useful if they are properly trained. First aid courses that are not advanced, often repeated can help but it really is nowhere near enough to think you are ready to even halfway towards the front lines. Often simple first aid courses can also make you think you know more than you do. That also commonly coincides with attitudes where people are not listening.
I just have absolutely too much experience with people making bad situations worse with their actions. And even some people causing emergency situations because of what they don't know. But I do not disagree with you. I think we are talking about two different things. I am talking about normal first aid courses people take every couple of years what you are talking about is actual advanced first aid courses that properly teach emergencies, how they work and how you need to act.
Of course, don't lay down. Really learn and train to become useful in those situations. You don't need to be professional, just properly trained. There are multiple ways to do it but you need more than a couple of days a year to also keep that training up to date.
I just have a lot of experience with people making things worse because they think the basic to medium first aid courses will make you able to help properly. And then make things worse. So my comment might have come out too harshly. But advanced first aid with the psychology of emergencies and scene management with the right attitude (mostly listening to those more experienced) will actually be useful.