Earlier quoted context omitted.
On-chain scaling is not sustainable. If you want to handle as many transaction as for example Visa, you would need 1 GB blocks every 10 minutes, which would make the whole blockchain heavily centralized because regular users won't be able to host full nodes to validate payments. About "adopting" and increasing block size. I think most developers agree that we would need to increase it at some point, but I believe cor…
Actually there is a great way to scale on-chain: UTXO Set Commitment allows nodes to simply discard unnecessary blockchain data (in a way not too dissimilar to classic "pruning"). The data set maintained by nodes would basically grow linearly with the UTXO Set instead of the number of txns. Eg. right now it would cut 150GB down to 3GB. Sadly it seems under-researched.
And it's not only an issue for end-users (can't run a bitcoin client on your phone, you'd burn through your data within a couple days), but also for miners. They'd be far more likely to mine on top of an old block, leading to stale blocks.
There was a talk a while ago how the bitcoin developers improved the propagation of new blocks within the network and it basically eliminated stale blocks (at least for a while).