> Maintaining a data center is much more about solving real-world challenges. The cloud requires expertise in company-specific APIs and billing systems. A data center requires knowledge of Watts, bits, and FLOPs. I know which one I rather think about.

I find this to be applicable on a smaller scale too! I'd rather setup and debug a beefy Linux VPS via SSH than fiddle with various propietary cloud APIs/interfaces. Doesn't go as low-level as Watts, bits and FLOPs but I still consider knowledge about Linux more valuable than knowing which Azure knobs to turn.