Nothing outside of mountain medicine and very basic first aid. Meds, ointment, gauze, and maybe a few other things like a skin stapler. Not king LTs or other airway stuff, not a surgical kit, not a bag valve, no decompression needles, no granulated quickclot or **** like that.
You said you don't go out much, and it's not a war zone. You don't need a actual IFAK. I mean that as in, you won't use it. It's extra weight and bulk. Chances are most of the people here who are about to "just in case" me probably don't have a fire extinguisher in their car…just in case.
To supplement my position, you're not going to put a chest seal on yourself. You're not going to pack yourself with impregnated gauze. If knowledgeable in things like a SOF-TW, then you probably already know how to turn a belt into a tourniquet.
Most people are carrying a trauma kit guised as a IFAK, to feed a hero complex, in case someone else needs it.
If my statement is true, then you have a responsibility to learn how to use the **** you plan on carrying around. That said, if you want the military doctrine of it, then the IFAK is actually so others can treat you. That's even worst, because now someone else needs to have the responsibility to know how to use your gear in question.
Frankly, I don't trust a single one of you to treat something like a gsw to the chest. I don't think people here know what to look out for, after using a seal for a sucking chest wound, and surely I don't trust anyone here to do a chest tube in the field let alone a needle thoracentesis.
Call 911.
Use a inreach. If you're far in the backcountry, this will probably be your own way out anyways, especially if immobile. There are risk we take in life.