It's a phrase. To fall in love with something means you enjoy it greatly. I got a new puppy and fell in love with him. I didn't like my new car but after a road trip, I fell in love with it.
My comment was about how many players who play few champions have one specific champ that they see and love all over, kit, design, aesthetics, gameplay, etc. I have never had that, I don't enjoy any champion in that way and I want to because I really don't have much fun on almost every champion.
But you clearly don't understand things like playing a character unlike you as part of the fantasy that Riot uses to design champions. I like Cho'Gath because he is the giant monster fantasy in a champion. Zed is the ninja master fantasy, Azir is the commanding leader fantasy. But what it sounds like you want is a self insert character, which in my opinion is boring because it lacks creativity in designing a great character. Examples would be the main character of Call of Duty who is a largely silent protagonist so that you can put yourself in the soldiers shoes. I don't like that. I want an interesting and well written character. But you probably aren't a writer so you don't see characters the same way I do.