Clarification with what Fizz Enthusiast said about Leblanc and "Kite Mage"
First of all, stop taking it so linearly. Keep in mind we're talking about AP Champs, and how they are distinguished in their playstyle. For that, I made a little spectrum to explain. (sorry if small.)
https://i.gyazo.com/073a089a8a7fce8518912c15e013937a.png
On one end we have mages, the other end assassins. When we're talking far left for mages, we think of champs like Brand, Annie, Syndra, Xerath, etc. Those are mages with no mobility, yet lots of damage, with some other aspect thrown in like Range, bears, or Damage on damage. Now, let's take a look at where AP assassins lay within the spectrum. Evelynn, Fizz, Leblanc, Akali Gragas are the assassin spectrum for AP Champs. They're focused on High Damage with fight-escaping-mobility normally being their other aspect.
This is where the spectrum part comes in. You can't think of the AP Spectrum as different boxes that clasify each different champ by "X" measure, because that is looking at each within it's own void. If you added fight-escaping-mobility to Syndra (let's call that FEM for short), but decreased her reliability or damage, Syndra would be much closer on the assassin spectrum, because those are aspects assassins have. Now let's look at the middle, where I labeled Kite Mage (Whether kite mage is the true middle doesn't matter, you get the point).
Ahri is a kite mage because she has mage CC, but not as good as real mages (Syndra Ult-AOE stun, Annie R) nor the Range of others (Xerath, Lux, Ziggs) but she makes up for that with FEM. This puts her smack dab in the middle, imo, because she doesn't have any of the far leaning left aspects of Mage (Lots of damage, CC, Range) but she also doesn't have the extreme damage Assassins can bring when not fully ahead, with less frequent Mobility (Ult CD for R, only speed boost for Q).
Ahri doesn't have any of the far extreme aspects of either side, but she sits in the middle, reaping the small benefits of all she has, hence why she is rather safe. Extremes to the left and right are normally much riskier, in exchange for being far extreme. So now we talk about Leblanc.
FOR SURE, Leblanc sits in the assassin Red spectrum. When Fizz En. talks about the changes they have with her, keep in mind of the spectrum. Leblanc has lots of mobility and damage, with a small about of CC. That already puts her much closer to the middle of the spectrum than others, due to that. Since Leblanc seems to be a problem, the choice needs to be talked about what aspect do they want to bring in line. Is it her CC that's the problem, or the Damage she's doing alongside the CC.
If they think CC is the problem, nerfing that pushes her towards the Right of the spectrum, back to the more extremes of it. If they think that Damage is the problem, that pushes her to the left, away from the extreme, but more towards the middle, the Kite Mage area. Just because they are pushing her more left DOES NOT mean that they're changing the identity of the entire champion. It means that she is simply approaching an area where she is more mage-like an assassin.
The red arrow is meant to show where she'll end up being after nerfs to damage, and the Blue arrow is where she is currently. She is still an assassin, but her kit and playstyle, that changed after the rework to rely more on E, now makes it so she relies on E to kill people, which is like Ahri, where landing E makes it easier to kill people, while dodging it can fuck you over.
Honestly, I just think that Fizz En. is inarticulate as hell. If I were him, I'd spend a minute or two rereading what i wrote to avoid misinterpretations, but also, possibly consider this. What if Fizz En. is talking to you, like he expects you to be on the same level of knowledge, of game understanding, as he is, talking to you like you're both equals?
TL;DR: Leblanc is still an assassin, she's just more near the middle then where she was before, due to her CC. Keeping her towards the middle is much healthier since it relies on less Extreme of a certain aspect to make a champ work (Hello pre-rework Talon).