There are two problems with downtowns, in a tiny city, giant city, whatever.
First of all downtown already has a purpose which is to extract middle class home equity, run it thru the retail and restaurant wringer where 95% of businesses fail in the first two years or whatever. Its easy for the city to run downtown; the city doesn't have to worry about parking, for example, because those businesses are designed to fail and new suckers appear as fast as home equity loans can be sold so they don't need parking for businesses that don't have customers LOL. This also becomes self fulfilling, downtown is for dead businesses so why would I go there unless I had to because by definition the businesses downtown suck or they wouldn't be downtown where businesses go to die?
Secondly the downtown has drunks, criminals, crazy people, panhandlers, drug addicts in various state of withdrawl, buskers, homeless, and many/most cities are constrained to the light touch, which is nice for those folks, but also means nobody wants to go there. Crazy people have to go somewhere, and downtown has the church mission and a park by the river and a liquor store for self medication. I'm not even remotely interested in hanging out with those people, so I'll go to the Target at the interstate exit instead, or more than a generation ago I'd have gone to a mall where security is at least not non-existent. Your example of a park bench will have a homeless person sleeping on it, the scenic pond will have a drunk peeing in it, the cafes nobody wants to sit at because of aggressive panhandlers and the smell of excrement from the streets and alleys... You're asking for the whites-only exburbs where the average sales price is above $800K to keep out the riff raff that's 30+ miles out of town, I live by those places and they're cool but unachievable for 90% of the population. I live in the 3rd richest suburb in my metro area and even here our downtown is dying, getting overrun. The economy of the future is clustered around interstate exits not some arbitrary place where a railroad put a depot 150 years ago.