Nope. It's just time and personal living space. It's THAT simple.
Go on, try to plan your day with transit and no car if you have 3 children (with 2-3 year age gaps). You'll find that this really works only if everything is concentrated, or if it's a full-time job for you. That's why we hear so much about "15-minute neighborhoods".
But when everything is concentrated, it becomes EXPENSIVE and you also lose any semblance of choice. You will likely have only one school, one daycare, one community center. You become hemmed in within that "walkable" neighborhood. That park nearby? It surely can look nice, but what if it's the only park within reasonable walking distance? So you don't even have an _option_ to go somewhere else with kids, without making it a full-day trip?
People like to laugh at Texas, about how riding an SUV to a walkable park is ridiculous. But is it, really?
The way to fix all of it? Suburbs and cars. Cars provide personal freedom and personal space. That's also why the US had a higher birth rate for much longer than Europe, and it started cratering once young people were forced (by the economy) to move into dense city cores.