I think some people miss the fact that the Phantom Thieves are playing right into Yaldabaoth's hands when they change people's hearts. They're basically proving that people need someone else to act for them and that people aren't willing to solve their own problems. Just look at how they end up sending their targets back into the depths of Mementos.

Don't get me wrong, the Thieves are doing good by freeing people from Yaldy's control and from their selfish distorted desires (which are just another form of control), but they are also showing that people are unwilling to free themselves from Yaldy's control on their own. When people don't free themselves, they only end up being imprisoned even further by society. That's why all the morally redeemable characters in the game change their own hearts, and that's why the Bad Ending is Akira deciding to keep society just as it is under Yaldy's control, with the Phantom Thieves as heroes who continue to change the hearts of individuals, but society as a whole is kept stagnant for eternity.

This is also why the public's support for the Thieves is so important in the final battle. Without their support, the Thieves couldn't have defeated Yaldy, because the public needed to show that they wanted their hearts changed, that they didn't want to be controlled after all. They all needed to show a will of rebellion against their oppressor or the Phantom Thieves would have just become the same thing Yaldabaoth was doing by removing their free will. Prior to fighting Yaldy the PT don't respect the agency of their targets, and they solve other people's problems without thinking about how that might affect the person they're saving. By defeating Yaldabaoth, they let go of that power and give control back to the individuals of society so they can start to change their own lives again. The public shouldn't and can't rely on Yaldabaoth to solve their problems, and they shouldn't and can't rely on the Phantom Thieves to solve their problems either.

And again, don't get me wrong, Persona 5 says that it is good and even necessary to get help from others, but if you really want to improve your life you need to act for yourself. If society is going to improve people need to take destiny into their own hands. Persona 5 is about finding hope even in the darkest circumstances by forging connections with other people and refusing to let society crush you under its heel. But the key to this all is that you must choose to fight against the cruelties of society, even if it seems impossible. Hope for change can be seen by finding belonging with others and working together to change society for the better. In the words of Morgana:

"Even if you feel that only darkness lies ahead...as long as you hold hands together...see it through as one...the world will never end!"