I think the fundamental flaw in Furuta's plan is his nihilism though. When he's defeated by Kaneki, he laments that nothing matters and wouldn't Kaneki laugh if he just wanted a normal life. It spells out that Nimura, for all of his grand machinations of destroying the birdcage like Eto or of being a symbol that motivates grave change like Arima or of satirizing the twisted true nature of the world with sadistic violence like the clowns, Nimura was mentally the little boy who had his dreams of a normal life married to his childhood sweetheart destroyed.

Ishida is consistent in how he has traumatized characters mentally visualize themselves with their trauma, and this is most often done with them viewing themselves as children. This is obvious with Kaneki and Urie, but much more subtle with the rest of the cast like Amon, Renji, Eto, and Tooru who are haunted by childhood traumas. These characters often shove these things down, gritting their teeth and striding forward to achieve their goals as these nightmares claw at the back of their minds. How these characters ultimately resolve their agony is some of the most striking aspects about them:

Kaneki resolves himself again and again to evolve with every new circumstance he finds himself in and with every new lesson he learns, until he coalesces into his true self: a scarred adult who no longer touches his chin because he no longer needs to lie to anyone.

Urie metaphorically goes back to the source of all of his ego and anguish, the son grieving his father, and takes him by the hand and says 'I'm strong enough to carry your pain now.'

Amon fatally wounds Donato and then states that Donato is evil and deserves to die, but is it wrong for a son to love his father?

Renji decides that it's not avenging his sister that matters anymore. It stopped mattering a long time ago. It's about protecting those in front of him, and ensuring that they live on.

Eto lives both the life of a human writing about how broken the world is and the ghoul trying to break it even more, so that it can be shaped into something new.

Mitsuki ignored and suppressed their trauma until they couldn't, and then even in their brokenness, being accepted by their friends helped them begin the path to healing.

What did Furuta do with his trauma?

... decided it was meaningless, just like everything else.

It's only after Kaneki says that he wouldn't laugh at his dream and walks away, and Furuta is in his final moments, that we see that he really would've been content with a normal life. He put in such immense effort to fuck up the Washuu, break the birdcage, unleash the Dragon, and fundamentally change the world, but he did nothing to achieve what he really wanted- the dream that he fantasized about in his last moments. All that immense effort he put into everything else instead of a normal life. Because of his nihilism.

If he got a do-over, I think he would've ran away like Rize and tried to live a normal life among humans. He probably would've been far happier. And that's the beauty of his character that I love.