> Does anyone else find it surprising that rockets are a century old[1] and yet still seem to fail spectacularly with amazing regularity, often due to some small flaw?

Not really. The performance metrics on rocket engines are utterly insane.

The jet kinetic power of a Merlin 1D engine at sea level is 1.3 GW. The work output of a nuclear power plant in a device weighing half a ton and costing maybe $400K.