I think they did literally make bricks from scratch as well as cut down/forage wood. It was another country anyway, so space was less of an issue but even there there is no way everyone could it. And, as you say, the small but very essential things like screwdriver parts and nails they needed from elsewhere. And those small things need a massive system behind them.
Humans ability to specialise and work together is our single biggest ability. I do think there's a balance to be found with efficiency. The most efficient way to live could be everyone in tiny boxes never meeting other people in person (space for meeting people is a waste) and just communicating online. All goods could be delivered via massive Amazon warehouse
Turn allmof South Spain into a big greenhouse for growing food and you can convert the rest of Europe into datacenters, tiny box houses and warehouses.
Pure efficiency feels quite dystopian. I like having countryside, i think we benefit from having farms and farmers and I think the loss of pubs, youth centres, and yes high streets is a tragedy. I think people would be less crazy if we had more and more pleasant third spaces. And high streets/their decline is a visible reminder to people of loss of "community". Which then gets transmuted into blaming immigration etc. So I don't think reviving the high street or alternatively trying to find a decent replacement for the high street is a bad idea.