The solution is obvious:

Remove commuting by encouraging remote work, incentivise dumb phone use or penalise smart phone use, create affordable property prices and secure future pensions, incentivise no televisions and create an environment where men and women can co-mingle naturally. You're right tens of thousands isn't going to cut it.

Basically apartment complexes with plenty of facilities like cafes, libraries, parks, restaurants and sports facilities and micro mobility solutions for transport surrounded by nature. Effectively reversing some of the trends we've established over the past few decades.

The reason this isn't done is because it wouldn't grow the economy, it would shrink the economy. You're effectively telling people to work less, have more leisure time and spend less.