Of course AWS is the mainframe in this analogy! It's a huge throughput- and reliability-optimized overhyped crazy expensive server that you hire someone else to run for you. It's designed the same way, with dedicated storage, compute and backplane servers. Even the discourse is the same to the 80s: "why we have to rent a $$$ monster when a $ commodity server outperforms it". How is this not obvious is beyond me.