I can offer contrast between where I grew up, Cleveland, which is not a vibrant city, and Los Angeles, where I live now.
In Cleveland, no one walks. It's jarring when I visit home now and sometimes not seeing a soul walking beyond the occasional drunk down on their luck, even downtown. Even the poorest people here save for a $1000 car, and they can manage it because rent is $400 and insurance is dirt cheap. As a result of all this non walking, most restaurants and shops are located in suburban style developments with hundreds of cars parked in the lot. These are extremely popular. The Eaton Chagrin shopping center, for instance, gets so much traffic the exit ramp backs up onto 271 for a mile and the parking lot typically fills up entirely. I've never seen traffic quite like this in LA, spilling out from a highway offramp directly into a shopping center and gridlocking an entire interchange. Things are slow during rush hour in LA, but traffic actually moves, you are never stopped for 10 mins not moving at all unless there has been a serious car accident.
As a result of all this nonwalking, the few commercial corridors that were built in the streetcar era perennially suffer. For lease signs are more common than open signs, but luckily these rare small lot commercial parcels don't get turned over for development into big box agglomerations very often since the population of the metro area has been entirely stagnant for 50 years. This means that every restaurant and every bar is a drive, and this is a drive you have to make yourself as sometimes it takes 20-30 minutes to wait for an Uber to make it's way to your neighborhood, given the low demand and low density of the population. This is a recipe for a neutered nightlife, neutered pedestrian life, and serves to further amplify the feedback loop of clearing more woods in the fringe suburbs for tract housing and developing more suburban shopping centers.
Because of white flight, the city never really recovered. Cleveland used to have 1 million people living in its borders, now it's 380k, and the city is remarkably hollowed out and many historical buildings have been razed for surface parking. Urban development has focused on getting people downtown for a sports game and nothing more. The bars downtown are a recent phenomenom, brought on by millenials being drinking age and having literally no bars beyond suburban family taverns, bowling alleys, and formerlly smokey dive bars to frequent.
Then the winter hits, and things truly die. No public events really happen, and people just stay in their homes and try not to spend much time in the cold. If they want to spend time in the cold, they drive 4+ hours to upstate New York where there are ski resorts that take longer than 30 seconds to go down the hill.
In LA, every single street has someone walking. Every major artery has a bus that comes at least every 10 mins during rush hour, and I made extensive use of the busses before the pandemic. In other words, because of this sprawling high frequency bus network, the streetcar feel of the city never went away. Commercial corridors are sustained if they are on a bus line with decent ridership. My bus stop was even able to sustain a man who would be there every day in a canopy tent, selling solely roasted peanuts and socks (I'd like to think he started with a wider selection then ended up refining his inventory to his best selling commodities). Also on that corner was a cell phone repair store that also sold excellent crepes, my barbershop, a fruit seller, several weekend vendors, two taco trucks, a pizza shop and night club, several filipino restaurants, four markets, and in the evenings a churro vendor. And this is a rather unremarkable corner in the Rampart Village at first glance, but teeming with vibrancy for the pedestrian.
I walk down a random residential street in LA, and I have good odds of encountering someone selling elote, or sliced fruit, or a truck selling whole fruit directly out the back. The city feels like it's teeming with life, teeming with entrepreneurs, teeming with small business. Before the pandemic, it was rare to see a vacant storefront. Even now, local businesses are doing a lot better than I anticipated and few are folding, versus Cleveland where it seemed like in any given commercial corridor that wasn't a brand new strip mall, vacancy might be 80%.
In short, a vibrant city is like a vibrant ocean reef. Teeming with all walks of life everywhere you look.