My experience of reading MN is that many people grow up in disfunctional families and have no idea at all what a normal loving relationship is like - whether between parent/child or friends or siblings or whatever.
So when they feel the normal attraction to another person in their teens they mistake this for love and think "you can''t help who you fall in love with right?" (I think this is actually a quote from another thread about abusive relationships) and then end up with some damaged person who they don't really love - just feel attracted to. Of course you can choose who you love - at the beginning certainly.
And yes love is an action. My children don't feel loved just because because I tell them so (although I do) but don't do anything that prioritises them. They feel loved because they see how important they are to me in the decisions I make every day. My parents didn't feel loved because I called them once a week and said so. They felt loved because I visited, went to doctors appointments with them, made them feel safe when they got old, were interested in them and their friends, included them in our lives.
I felt loved as a child because my parents told me they loved me, hugged me, kissed me good night, provided for me, made sacrifices for my education, welcomed my friends into our home, knew when I was upset, did things as a family that I still remember - breakfasts in bed together, helping out on meals on wheels together, walking the dog together.
"Romantic" love isn't that different. It is about how you treat the person not how you claim to feel about them.