From how I read XY's story
Tl;dr: Lysandre thought the world was overpopulated and was suffering the effects of such (like people fighting each other for limited resources or stealing from one another). I believe that's what the NPCs trying to claim he had a point where referencing.
He thought this behavior was ugly on the world and his idea of beauty was to reduce the world's population in order to create a big enough resources to people ratio for people to no longer fight among each other, steal limited resources, or even have to share materials. This is made somewhat explicit during the climax. Additionally, there was a backstory saying he tried to help others but got taken advantage of in return, and this is where he got his enragement towards humanity as a whole. Sycamore sees where Lysandre got the point in claiming the world was overpopulated, but suggested he could've tried using his role to develop more resources instead of eliminating other people. What Lysandre actually did is a typical villain route to carry and I find it works because it ties to a major backstory that's somewhat deep for a Pokémon game, then connects said backstory with the mysteries of Mega Evolution and the roles of the Legendary Pokémon on the front of the cover, which are what the Pokémon games are about.
I believe X and Y had a lot of fluff but the general premise of Team Flare and their visions were rather simple. Nothing as deep as what many are trying to make it out to be. I believe the reason Lysandre chose to keep Team Flare is because when you have a mass murder weapon that you're planning to use on a global scale, you can only really defend those near you, and Lysandre isn't necessarily Thanos. He couldn't just wipe random selections of the world out of existence. He wanted it to be hard to fit in since his vision was to reduce the world's population by a significant extent, so he charged 5 million Pokedollars to enter.
Ironically enough Lysandre was trying to stabilize the sustainability of populations in a way he saw fit when this was precisely the goal of Xerneas/Yveltal/Zygarde. He tried to play them, to play gods, with a weapon that channeled their energy, only for said gods to suddenly break out of the machine upon waking up then dunk on him.
Idk I just have this placed down to provide my own insight on major parts of XY's story
Instead of engaging with the interpretations you disagreed with, and explaining your disagreements, you laid out a surface level, Wikipedia-style plot summary (bar the bit about the legends) that still misses and misunderstands explicit text. Even if it was correct, there's no reason multiple interpretations couldn't exist simultaneously.
For the sake of clarity, I'll point out why specifically this interpretation is incomplete and incorrect. Here are the major holes.
1)
Tl;dr: Lysandre thought the world was overpopulated and was suffering the effects of such (like people fighting each other for limited resources or stealing from one another)
Partially wrong, partially right. Lysandre does not believe this early-game, but he does believe it late-game.
Early-game Lysandre:
"Kalos is beautiful right now! There will be no foolish actions if the number of people and Pokémon do not increase. That being said, the future isn't decided. You can't be sure each day will be like the one before."
Some kind of change happened to take his beliefs from "Bad things may happen in the future, but the present is fine!" to "The present is not fine / doomed to become so, and requires immediate action!", which he does believe later as you say. The game drops hints at the cause of this change, most explicitly when Sycamore says Lysandre couldn't put his ego aside after his defeat. I integrate those hints more fully in my post.
2)
I believe that's what the NPCs trying to claim he had a point where referencing.
True in isolation, but the way you make this claim is misreading the room. Our problem with "Lysandre had a point" dialogue was not "it doesn't reference anything plausible." Our problem was that saying stuff like "We should meet Lysandre halfway!" is, on its face,
nonsense. There's nothing to justify "We should meet the mass murdering terrorist halfway." Even if a line like that had good intentions and ideas that can be saved, it needs some kind of change to better express itself.
3)
He thought this behavior was ugly on the world and his idea of beauty was to reduce the world's population in order to create a big enough resources to people ratio for people to no longer fight among each other, steal limited resources, or even have to share materials.
Lysandre was trying to stabilize the sustainability of populations in a way he saw fit.
Very incomplete. "He was doing what he thought was right" is an overly simplistic understanding that misses key explicit detail from the text. At multiple points, the game explicitly and implicitly prods you to think critically about why he got here, and the mistakes he made along the way. Understanding these mistakes is key for understanding the story. I'm not teasing out subtle explanations here, the game is just telling you right up.
Here are some points of textual evidence:
A) Diantha directly challenges his idea of beauty, calling it ridiculous. (Café Soleil)
B) After Lysandre tells you that he tried to work all on his own (Lysandre Labs) and implies that seeking help from humans is demeaning (Team Flare Secret HQ), Calem / Serena tell him directly that he shouldn't worry about the future all alone, and that he should work together with everyone, not on his own. (Team Flare Secret HQ)
C) Sycamore tells you directly that he was egotistical. (Couriway)
This selfishness angle is also supported by a use of call-back I find cute. Note the similarities between the following dialogues:
Early on: (Lysandre Café)
"People can be divided into two groups. Those who give... And those who take..." "I want to be the kind of person who gives... But in this world, some foolish humans exist who would show their strength by taking what isn't theirs.""They're filth!"
""Long, long ago, the king of Kalos sought to take everything for his own"
Later: (Lysandre Labs)
That's why I decided the only way to save the world was to take it all for myself."
Notice how the giver became the taker, became what he once called
filth! ? The descendant of the king of Kalos has, metaphorically, become the new king of Kalos. It's a clever bit of foreshadowing.
4)
Sycamore sees where Lysandre got the point in claiming the world was overpopulated
Mostly wrong, assuming you refer to the Couriway Town dialogue. He says overpopulation "maybe someday" could happen, and doesn't give any credence to Lysandre's belief that it is happening right now.
5)
He couldn't just wipe random selections of the world out of existence. He wanted it to be hard to fit in since his vision was to reduce the world's population by a significant extent, so he charged 5 million Pokedollars to enter.
Underbaked view. There are a zillion possible ways to pick a small subset of the population to join his organization. He could hand-pick some people he trusted, or those that were especially competent in some way. He could pick a random subset of the population to become Team Flare members. He could find people who did public acts of kindness to prevent the kind of greedy world he feared from repeating itself post-weapon.
In a world of all these options, he:
1) Picked the kind of selfish, greedy, and unproductive he people complained about (Team Flare members);
2) Picked people not for their personal skills to work
alongside him, but for contributing money that
he could use to do the heavy lifting on his
own;
3) Picked people on the basis of funneling large sums of money to himself, evoking the greed he complained about;
As a narrative choice, do you think this is a coincidence? That he just happened to use this method to recruit a small subset of people, instead of any other I mentioned? I do not think it was a coincidence.
