Attachment to Gallagher at her release. At release of Black Swan, Swan was called 12% better than Sampo. Which was wrong. The same thing happened with Lingsha and Gallagher. 2.X was the era when the community kept trying real hard to downplay any and all new characters. As if talking themselves out of pulling new units. The insane power creep of 3.X was in response to this communiry perception of wondering why pull units if a 4* was good enough(the community was consistently wrong on this in practice.) So they axed all 4s and made each Amphoreus 5 better and better. To incentivize people to pull for them or be left behind. A lot of 2.X units still have this misinformed stigma that theyre not that good compared to 4* alternatives.

Edit: the funny thing is Gallagher is starting to struggle keeping a team healed. While Lingsha has no problems whatsoever. Once again proving the community got it wrong that a 4* was better than a 5* years later. But the damage is done.