An international KYCed or non-KYCed platform, open to all nationalities, where you can use your day-to-day credit/debit cards or wire transfers to buy BTC through Lightning and sell back to it. It can also host a marketplace (think ebay) where people can sell their stuff for BTC and start accumulating it.

Sounds too extreme to be feasible but this is the only way for a wider adoption and ultimately a true open & decentralized world.