To validate internally means to do this; say to yourself "what other people think does not matter, I know what I think and thats period. So I shall assess myself only by own my standard'.
Introverted Feeling cannot do this. In order to hold such an attitude one must be an autonomous thinker, this requires logical reasoning capabilities which Introverted Feeling does not provide.
Inevitably introverted feeling requires emotional support in order to feel validated, this necessarily derives from the outside.
Introverted Feeling however, is stimulated most easily by the internal world, (though paradoxically the content of the inner world derives from the external world almost indiscriminantly) but because it lacks autonomy of thought it cannot be validated by the internal world. It therefore, just like Extroverted Feeling, requires external stimulation.
Because both Feeling types are unable to be autonomous, they rely on others for support. This leads them both to make attachments to people, which forces them to care about others.
In conclusion, your thesis that Fe prompts one to care about people and Fi does not is untenable.