So, the question is, if all blockchains were suddenly to become scalable, would this solve the lack of user activity? I don't think so, there are tons of other problems, and most importantly, general population is just uninterested in blockchain.
I don't think it's that people aren't really interested in the blockchain, because they are and think it will be huge which makes them invest in this space, but there is no actual use to back it up.
In most countries people don't need crypto currencies because their regular system does its job well enough. We may think the regular system sucks, but if the average joes don't see it as such, they won't come over.
In order for people to start using crypto, the regular system needs to mess up so hard, that they have no other option than to adopt crypto currencies. Bitcoin's white paper popped up during the credit crisis with a reason.