I see Fi as responsible more for why we want to do something than what we want to do. This is the big, underlying values-based "why", not the why that is answered by showing how doing A is a means to achieving B. Yes, it is a key component of motivation.
Thats pretty much exactly what i said. What i didnt say was the part that Te has in executing the drives that Fi gives and Ni shapes into ideal image.
"Where wisdom reigns, there is no conflict between thinking and feeling."
— C.G. Jung
I agree. The most common stereotype I have in mind for INTJ (which is usually true) is the cynical idealist who has learned to repress their idealism beneath a cold exterior.
This is how I see INTJs too however all intuitives are idealistic. The difference between NTJs' and NTPs' idealism is that the Ni-Fi leads to internalisation and attachment to ideals and Ne-Fe leads to depersonalisation of ideals which is explains why NTPs are less cynical.