This is ironic, right?
Eri's quirk was foreshadowed through the entire Yakuza arc. The only other type of quirk it could have been that hasn't already been was that or just the ability to destroy quirks, the latter being a disappointing reveal since it's basically just a better erasure. The one time she used it, she killed Deku.
They suggested using her quirk on Mirio, but that's a horrible idea since her DNA was used to remove his quirk in the first place.
They also established they don't want to use her quirk again, or at least not for a long time, because it's deadly, harms her and nobody understands how it works yet.
There are plenty of characters like this with the same established restrictions, and they're usually let off the hook, but people have to lose their shit over Eri's quirk because... They're speedreaders?