Yes I agree that currently block size is just a quick fix. However I also think that propagation speed can and will be improved one day. Communications have seen tremendous improvements over the years. Although that's a longshot I admit.
However, the Bitcoin network is already at 50% capacity, in a bear market. How do we expect adoption to spread if people won't be able to even transact between exchanges as soon as users double? A quick solution is definitely needed.
What about mimblewimble, do you think it could work?
Yeah propagation speed will inc but not enough to scale. You could use a second layer 0 base layer solution such as bloxroute that aims to fix the propagation issue. The problem with bloxroute is it skews chain interest by creating a new network interest-yikes.
Communications has increase but they also use second layers as well :P Exp, sharding is pretty big in database and other solutions.
To be fair centralized solutions could be done to transact between exchanges.
Mimblewimble is actually a pretty good solution but even they are working on second layers. Mimblewimble is also less feature rich so if you think Bitcoin has limited smartcontract features well Mimblewimble are way less....