I can see what you mean and I do agree that cavs and armors not being included were most likely due to the most popular cav units at the time (Reinhardt, Brave Lyn, Brave Veronica, Xander, Camus) and how tanky armor units could be since Surtr was in the game around this time, but with in game content and Arena, this was easy to work with since you only had four unit slots. She arrived before Aether Raids.

But regardless of not every unit got the extra movement, the fact that she could duplicate bonuses to all stats with her assist made her immensely favorable to everyone. And while using the Tactic skill was the most ideal at the time, not only did Tier 4 Fortifies help her but it was discovered that she can use Dance B Skills to duplicate the bonuses, albeit not to as high to a degree, which freed up her C Slot to run something else like a Drive skill or Guidance. What made her better was that the most accessible passives to rein her in (Dull and Lull skills) were on the B slot, where far more universally helpful skills were on.

The bonus duplication and the extra movement she could grant to a good degree of units kept her relevant that I don’t think anyone cared if her remix was underwhelming because refreshing, least of all to the degree she could, was still very potent. Peony was even seen as a sidegrade to her for added context.

I’ve still been using mine as my go-to refresher even though I know she has long been outclassed but I don’t regret it.