1. "Loving someone" and 2. "Fall in love for someone" are NOT the same thing (we could call them the 1. "Quiet" and 2. "Exciting" types of love).
Alas, our romantic culture tells us only the second kind is the REAL love. All the while forgetting to say that this second kind is usually temporary (on average it lasts 6-18 months).
Thus people not feeling it (or not anymore) think something is wrong with them, or the relationship, or the partner.
IMHO, the "Quiet" type is as true as the other - and maybe more. It's usually deeper, and often longer-lasting. It's what most loving long-term couples feel for each other: the Excitation is gone, but the Love is still there.
I think we should better learn to appreciate BOTH of these kind of love, with their diversity; and stop considering one "lesser" than the other.