The author ignores that large cloud providers design their own hardware. They are not using generic systems, but are designing their own. My own personal hypothesis is that the "servers" that run the major clouds will converge on something that looks like mainframes.

They won't be mainframes, because as the author does correctly point out, mainframes are unmatched at large-scale, high throughput, resilient, stateful, transaction-heavy workloads. While that is part of what the major cloud providers support, it is not everything. Because it is not everything, the systems the major cloud providers design and build will look different from mainframes, but I think they will have key similarities: virtualization and security features provided by the hardware; high reliability through redundancy and in-hardware error-checking; easy physical maintenance through hot-swappable components.