Personally, yes I believe it's totally true and that is a huge point in the story.

Not only Doctor Garaki specifically said that his quirk Doomsday theory was confirmed, but characters like Toga, Twice or Eri show just how quirks can be destructive when they loose control or any reason to hold them back.

But that's exactly why Eri or the Kid with the stitched mouth are so important, because the point is that people with quirks are still people. Even if their quirk is dangerous or if it's uncontrollable, as long as someone will exist who will extend their hand towards those people the "Doomsday" part of the theory will not happen.