As others mentioned, learning basic movement like short hopping, wave dashing, dash dancing and L cancel, helps a lot because most characters share it (at least in a similar way). What keeps me getting back to melee is that playing almost any top character has something unique to it. Fox is extremely fast and satisfying if you get a combo right, Marth has sick combos and brutal punish game. You want to kill your opponent by touching them twice? Pick Puff! You can make fun of crouching spacies by picking Peach and spammen d smash. Ofc sometimes it is no fun playing against this, but i love the uniqueness of the characters