This is partly true, many players who come on here tend to magnify League's current problems and forget how far we've come, which is why you get posts asking Riot to buff back assassins back to pre-rework levels of instant burst, when prior to that they were almost universally called the worst-designed class in the game. I've also seen a lot of posts waxing nostalgic about Season 2, calling it the best in terms of balance, diversity, design, etc. when it was arguably the worst in all of these respects, as it was the season of the Metagolem, where anyone who could abuse that extremely rigid build the hardest (i.e. fighters) turned into unkillable, hyper-snowbally damage monsters and dominated everyone else, where mages were nigh-unplayable because Force of Nature hard-countered them, and where Riot maximized speed of champion production over quality, generating kits whose problems still persist to this day (e.g. Elise, Fizz, Rengar, Volibear, etc.). Basically, as a collective here we tend to think League's current state is always the worst it's ever been, look upon its past with rose-tinted glasses, and therefore sometimes make some pretty questionable demands.
However, I think in LeBlanc's case it's not entirely unjustified, as from what I've seen her criticism addresses her design, more than it does her balance: LB seems to be at a pretty okay power level, but her playstyle has been turned into that of a waveclearing kite mage, when pre-rework she was an all-in assassin with some mage elements and poor waveclear (the devs had also specified that they didn't want to alter this, even if they did want to space out her burst). Not only has this upset many of her core fans, whose favorite champion got their playstyle essentially flipped, but it's also not the best design for anyone else to deal with, as LeBlanc has so much free-targeted mobility that when she can use all of it defensively, she becomes practically impossible to reach for any champion with less range or mobility. What many players might be signalling as a result is a return to a playstyle that better embodies the old LeBlanc, i.e. an emphasis on going all in to burst down your target, rather than a full revert that would include her previous lack of counterplay.
Come to think of it, this could likely be a good topic for a megathread, seeing how there's a lot of discussion around this and mixed opinions. I can't speak for Leblanc's mains, but I do think it could be useful to gather feedback from them to better understand their grievances with her current kit, and how they want to approach future changes in order to move closer to a playstyle they enjoy, while still allowing for interactivity and counterplay on their champion.
kill faster than current champions such as 
for example.
