The concept of shifaat is about intervention by something or someone for something or someone for a purpose. In the quran it is made amply clear that each person is individual and is held responsible to face consequences for one's own beliefs and actions. However there arise situations and circumstances whereby more than one person may be fighting for the very same end goal. It is in this context that word shifaat is mentioned in the quran ie people supporting each other for furthering cause of islam because they all believe in the same cause in the same sense.
Likewise shifaat is about mediation ie something or someone coming in between something or someone for a set purpose. For example, you are trying to pick up a hot pot so you take a piece of cloth and put it between your hands and the hot pot to stop yourself from getting burned.
Likewise influencing each other towards a goal is intervention or mediation but I doubt the quran uses word shifaat to get people off the hook for their wrong beliefs and wrong deeds. All must face consequences for their actions ie you put your hand in fire you burn it. All one can do is save you from burning your hand but they cannot save you from the set consequences. Prophets and saints can save people from kufar and shirk by trying to educate people out of it and only if they listen otherwise people will get what they deserve and none can save them.
So saving is only possible at action end and not at consequences end.