Well there is a reason the first city that trialled the 15 minute thing was in a Tory council area. That way they could couple it with making things terrible for cars, while not sufficiently providing public transport as a replacement. All of a sudden, what would only be a good social development providing more services nearby (that might also hamper large business' control of retail markets) now became associated with something generally harmful to common people.

All a 15 minute city is supposed to achieve is sufficient access to general things (eg small shops and parks) spaced frequently enough for pedestrians with infrastructure (segregated paths) to safely travel between. It's literally just the culmination of professional city planning philosophy. That doesn't even mean cars need to have reduced access, just that their priority would be inherently lower - you wouldn't need them as much. However, they structured the trials to portray it as something else. It's basically what they did with the AV referendum, which is construed as support for the FTPF system.

The hilarious thing is that they weren't even successful. The botched implementation of Oxford as 15 minute city was still objectively better. It was extended, until a Tory councillor axed it.