Her range is fair, considering she has an AoE blind and a good gap closer. If you think about it, the three adcs that Quinn is most similar to are Lucian, Graves, and to a lesser degree, Vayne. All of these have shorter range than other adcs, because their kits are just so good.
If Quinn were a little less buggy and a little more reliable, I think she'd be in there with those three, with perhaps a somewhat smaller niche because of her ult.
What she really needs are some bug fixes, and maybe a few small QoL changes to her ult (but, bugfixes first).
What we really don't want is for her to suddenly burst onto the scene with too much power and get nerfed into oblivion because top laners start complaining. Whatever Riot does, they should do it slowly, and steadily, and stop when it's enough.