critique:  Bitcoin can only support around 7 transactions per second, so it will never be a global currency.

rebuttal:  Bitcoin's base layer today can indeed only support a theoretical throughput of 7-10 transactions per second. This is vastly less than the ~4000 tx/sec that the VISA network can hit at peak times. But bitcoin transactions are not VISA transactions. Bitcoin today settles over $5B in transactions per day across hundreds of thousands of transactions. This simply means a much higher average transaction value (over $5,000) vs retail payment networks (VISA's is around $80). Bitcoin is much more akin to a large value settlement network today, than a retail payments network.

The core nature of a bitcoin transaction means any amount of value can be transacted using the same number of bytes and bandwidth. Given its core use today as an emerging store of value (see critique #8), it makes sense that average transaction value would be high, but sheer number of transactions per day would be a lot less than existing global payment networks. Global high-value independent settlement, that works anywhere, doesn't require a middleman, and credibly cannot be reversed, is a unique and high-value use-case that bitcoin alone occupies today.

In the future, advancements such as bitcoin's lightning network may offer a very high throughput way to issue bitcoin transactions, allowing bitcoin to scale as payment network, and even offer new payment use-cases not practical with traditional networks, such as machine-to-machine micropayments.