So "all" doesn't always mean all then.This is a false form of argument, in this verse the "all" pertains to those "in Christ".
who is the "we" and "us" in the verse?But in Isaiah 53:6 the "all" pertains to all that have gone astray, and "every one" who has turned to his own way. This means 100% of men, and says the iniquity of 100% of men has been laid on Jesus.
True, you have to look at context. Context determines what universal terms like "all" mean.Just because you can find verses where "all" does not pertain to every man, does not mean in all cases the word "all" never applies to all men.
So, who are the "we" and "us" in the Isaiah passage that pertain to "all"?