> Jet aircraft were actually flying by the 1940s, and those engines were built using the relatively primitive metallurgical and manufacturing techniques of the day
Yes, and the Junkers Jumo 004 jet engine used in the ME 262 "only had a service life of some 10–25 hours" (!) after which time it had to be replaced [0]. Admittedly German industry lacked raw materials to do better metallurgy, but in the 1940s there was a long way to go in terms of designing jet engines
Jet engines today are also routinely torn down, inspected, and rebuilt if necessary - much more often than piston engines are, I gather. But that's because of the overall materials stress and the necessary safety factors involved, not because of any general mechanical complexity. I mean, I guess you can count having all of those individual blades as being "complex", but in reality these are just the parts that make up mechanically simple fans and compressors and such.
Yes, and the Junkers Jumo 004 jet engine used in the ME 262 "only had a service life of some 10–25 hours" (!) after which time it had to be replaced [0]. Admittedly German industry lacked raw materials to do better metallurgy, but in the 1940s there was a long way to go in terms of designing jet engines
[0] https://en.wikipedia.org/wiki/Junkers_Jumo_004