A '15 minute city' is an hypothetical city wherein everything you need is found withing just a 15 minutes walk! First, I find no problem with such city unless the government use this 'no need to move further than 15 minute walk' to restrict movements. This will be equivalent to living in '15 minutes big' prisons or paddockings! You will be treated like cattle in zero grazing!

Another argument against a '15 minute city' is that people in marginalized areas can be locked out, and so make the poor poorer. But this argument is inherently misguided because a lack of services in marginalized areas means that it is not a 15 minutes city! A '15 minute city' means 'you don't need to move anywhere because everything you need is within 15 minutes walk reach'. To create a truely '15 minutes city' means there is no more 'marginalized areas' in the city!! An area is 'marginalized' because 'there are no services' in that area.

So maybe the question is whether such a utopia is practical in any foreseeable future! It is not practical because the very reason humans opted to live in cities was precisely because such '15 m cities' were impossible! We live in cities so few 'services centers' can serve as many people as possible. A city with '15 m' compartments is no different from small towns of '15 m' radiuses but that are far apart. Or in short, living in a '15 m' area is no different from living in a village! So '15 m city' defeats the very purpose of a city!