I don't see the appeal, these pairings are badly one sided and completely hollow in reliability. NaLu and Gruvia are the most gimmicky and underdeveloped pairings that put them as a couple, and they are completely one sided from the girls part. They have zero romantic chemistry and like all shonen come off as like Naruto and Bleach, last minute.
It's as if SasuSaku and NaruHina fans kept the band wagon on from when Naruto pairings were hot back in the day. Also Gajevy is completely weird as hell. Considering once Gajeel went Bobby Brown on her and after that was like the former pairings, none of them showed me they gradually grew to accept and love each other.
Same with Jerza, same with Mavis x Zeref. Only couple I accept is the gun woman and her husband and child.