The problem is your bolded statement. I'm just stating that ISFJs on average tend to not understand INFPs particularly well (it's half belief/half conjecture). It doesn't assign blame. If the statement is true then it is a simple fact.
The problem with the view you are voicing here is that it is critical of people who don't comply with this "standard" you are referring to. Therefore, those who do not comply with the standard ARE being blamed. By you. It comes across as a negative judgment of the other person vs. understanding and accepting them for who they are.