alt Hacker NewsThe throughput is arbitrarialy limited by bitcoin's current block size, which hasn't been increased since satoshi's era.
Most cryptocurrencies have an adaptive block-size mechanism which allows the blocks to grow to a reasonable size which could facilitate such an onboarding of users. So it isn't a technical problem, it is just a question of bitcoin's current leadership, which is controlled by companies like blockstream.
People have been debating the blocksize for a very long time now and there doesn't seem to be any large desire to change it so while the ability to increase it exists changing anything that fundamental about bitcoin seems to be a non-starter and while that is true lightning is pointless as a solution for the masses.
Even if you increase the block size 100x though you're still not improving the numbers much since my very generous numbers ignore activity outside of lightning and assume a single on chain transaction for every user and a perfect network.