This is more or less already possible. You can create a focus mode that only lets certain critical apps through. Of course the bigger problem is having the discipline to keep it on and not randomly pull out your phone anyways. And Apple (or anyone else) cannot fix that part.
I experimented with focus modes a while back and found them lacking. Does what it says on tin but I guess I was after Do What I Mean, i.e. I wanted my phone to figure out what was important for me. Maybe I’ll revisit them!
