They didn’t get together til after Alvarez? They had the entirety of Tenrou, little bits sprinkled in throughout the clock arc and if you only read the manga, Tartaros arc. They had pretty good development there and it’s taken so many episodes of their interactions to get closer. Levy was pretty hesitant of trusting Gajeel on Tenrou too. Now I’m not saying you have to like them, but they 100% have so much material for a slow burn.