>>529809989
Her problems are individually ranging from "meh" to "pretty bad" but they compound on each other.
Lupa's personal damage is low. This is meh. She's a support, so this is fine, to a point. The actual problems start with:
She's meant to support Mono-fusion. This is less than ideal mostly because it leads into the next problem.
Fusion is not well supported in terms of its roster. The only limited carry you have access to is Changli and the only support you have access to is Brant, who has by far the least ownership among the playerbase.
So if you want a fully strapped, supported preem team, you need Changli (easy enough ask) and Brant (Tougher ask cuz he was an easy skip for a LOT of people at the time).
Without both those characters, Lupa loses a good chunk of her buff value. Of course, you could sub Anko in for Changli or Brant but at that point you're putting a bandaid on a bullet wound.
Lupa was released too early in a state where the roster of the game can't make good use of her support, and her personal damage isn't high enough to make up for the difference. I have no doubt a Lupa team could clear, it's just gonna be sloppy compared to any other fully strapped preem team. She's purpose made for any future limited fusion resonators they'll put out soon. Probably Galbrena.
That's the long form. Short version is Kuro released a character with strictly future characters in mind and not so much the current roster and Lupa suffers for it. She's meant to support characters who aren't out yet.