I think she still has the potential to be extremely oppressive, but the margin of error keeps tightening on her. She's becoming an unreliable pick for many people that kept her in their mid lane rotation. I can see how this would frustrate a lot Leblanc mains. It's a very high risk for a high reward, but to people that used to play her frequently I can imagine it seems underwhelming compared to before.
I think champions like Leblanc are broken. Assassins in general can use some reworks. A super oppressive champion that can burst down people in a few seconds will always be hated, and there will always be problems with their game play because there is virtually no counter play when they land their combos. Their weaknesses are that they are squishy, have little to no utility (except for Ekko, but I don't consider him all that oppressive), and they need to take a risk to take champions out.
The only way to nerf these types of champions is to introduce more risk into an already very risky play style. This creates problems for many who play her, and if she ever got buffed up again, people would complain that the risk is not high enough for the reward Leblanc gets. It's like being on a seesaw where nobody is ever happy with the outcome.