Blockchains don't need to take over a substantial percentage of economic activity to be useful. I don't understand why people bring up transaction limits as if they permanently cripple the technology.
The throughput capacity of Bitcoin, being programmable money, isn't a user limit. We can just as soon put billions of users with BTC-denominated accounts at higher layers of abstraction, and in fact this is exactly what Bitcoin's core developers aim to achieve. It doesn't make any sense to globally broadcast every last Starbucks coffee and permanently etch it into an immutable database at enormous cost.