Why aren't Montag and Mildred in love?

In Part One of the novel, Clarisse rubs Montag's chin with a dandelion and mentions that he is not in love, because the dandelion particles do not rub off. Montag initially protests Clarisse's declaration and insists that he is in love with Mildred. Later on, Montag comes to realize that Clarisse was right, and he is not in love with his wife. When Montag asks his wife if she can remember where and when they first met, Mildred tells him that it doesn't matter and cannot recall. Montag then acknowledges for the first time that he is not in love with Mildred. Bradbury writes,

Well, wasn't there a wall between him and Mildred, when you came down to it? Literally not just one, wall but, so far, three! And expensive, too! (21).

Essentially, Montag is not in love with Mildred because they are on two different wavelengths and do not share the same interests, thoughts, or views regarding their society, entertainment, and literature. Montag is a troubled soul, who desperately wishes to change the trajectory of his life by pursuing knowledge and reading literature. In contrast, Mildred is an ignorant, superficial woman, who is addicted to sleeping pills and her interactive parlor walls. She turns to pills and suicide in an attempt to solve her unhappiness instead of analyzing her meaningless life and making a change. Montag recognizes that he is not happy or fulfilled in life and has nothing in common with Mildred. She is the epitome of everything Montag despises about his society. Mildred is callous, ignorant, shallow, and cold, which are significant reasons as to why Montag no longer loves her.
Even when Montag desperately tries to save his marriage by encouraging Mildred to read, she refuses to give up her shallow life. Montag's personal development and Mildred's refusal to change drive them further apart until Montag acknowledges that he is no longer in love. Eventually, Mildred calls in an alarm on Montag for owning books and dies when the atomic bomb decimates the dystopian city.