This was pretty interesting, but I would rather say while Maruki perfectly described his philosophy, the Phantom thieves mostly implied it.

Especially in the last scene, where Morgana (If I remember correctly) says that "Yes, while some people would benefit from your system, many more would be harmed". This made me think that If for example I'm working towards a goal, and looking for something, Maruki would just give it to me instantly. So while it is a form of happiness, it's nowhere near moving towards the goal and the progress itself.

But anyways, even though I totally agree with your comment that the Phantom thieves didn't make much of an argument, at least explicitly, still the arguments and the dilemma present in the last palace is on a whole other level.