But why can't Ontario have a town like this? Why can't we get 5000 people to kickstarter a town? Have really strict building codes and really pro-human policies.

Edit: What town are you, if you don't mind my asking. I'm planning on going back to Europe at some point.

To answer your question, it is because sprawling car-centric localities are the cheapest way (in the short term) to maximize the living space/cost ratio. European style cities don't spring up from empty fields anymore because they are more expensive to build. Your comment about building codes is telling. European cities did not form in the way they did because of building codes. They formed for economic reasons in a pre-industrial era. The same way American and Canadian, and newer European cities sprawl for economic reasons. That you bring up building codes is a tacit acknowledgement that to make a medieval city layout now would require forcing builders and buyers to pay more than they would otherwise.

Anyways, a medieval city layout nowadays would still be an inauthentic pastiche, sort of like a Tudor-style Celebration, Florida. Form ever follows function, and all that.

Once you change from thinking "oh we just must have cars here" to thinking "how would we solve problem x without cars" the whole city can be made to be more vibrant. We can't let our children out of our sights in modern cities they're so dangerous. That's madness!

In terms of authenticity, here I partially agree with you. I do not intend to emulate an ancient European city. That's dumb. But I don't want the city to end up looking like shit like most of Canadian cities do with their completely mismatched building styles, billboard ads, tacky chains, and telephone poles all over the place. Instead, at the city formation you get good estimates of what types of natural building materials are near by (the types of wood, clays, stone, etc) and you hire teams of architects and city planners to design a set of cohesive style guides. There should be room for custom flourish, but the city should still look like a cohesive whole. There is no reason to use concrete for anything other than subterranean piles. Use large flat rocks for streets. Yes rock streets are more expensive but they look much, much better and because we have density from day one they might be 10x the price but we should only need 1/10th of the pavement by area.

Also, by creating a hard perimeter around the city, there could be a real set of community gardens just outside of the city for things like herbs and other expensive plants. We wouldn't have to choose between city life and connection with nature.

That has nothing to do with cars and everything to do with culture. I grew up roaming freely on streets filled with cars in the 70s/80s.

Banning cars won't fix helicopter parenting.

https://en.wikipedia.org/wiki/Laurie_Baker

https://en.wikipedia.org/wiki/Christopher_Alexander

Some actually did. Lisbon expanded rapidly in the 1960s, and the new construction was designed on purpose to be 4 or 5 stories high with shops on the ground floor and with primary schools and churches as main foci of community interaction. If anyone wants to check out Google Streetview, the neighbourhoods northwest of the Zoo and east of Campo Grande park are typical.

But in America it seems that no architect made it back alive from WW II, and that's why their cities are so awful.

And part of the reason for that is that many towns buy an off the shelf municipal code called municode to start from.

You can get close, but it is expensive. You'll need pedestrian tunnels. Given that people won't be on the streets, you don't need to be concerned about traffic on the streets.