Nothing is for ever is a nothing but a (Well known) phrase, as has been pointed out, a large proportion of warbirds are virtually new albeit using old technology, however they all have more manhours spent on meticulous maintenance than they ever did operationally.
I wish people would stop going on about old technology, its a metal rivetted structure as used in everything from 737's to the latest aircraft, there is no difference bar stuctural stength for pressurisation and the Spitfire had that, the only really new construction technology of late is Carbon Fibre.
Heck you can even look at glued fuselage and wing structures used on the likes of the BAE 146 and that is using WW2 redux as the adhesives.
http://www.adhesivestoolkit.com/Docs...es/P3r9pt2.pdf
Remember the Comet / Nimrod first flew in 49, a scant 4 years after the war. The Typhoon took 20 years to gestate, you could argue it was out of date when it finally reached operational staus.
As for instrumentation, its only in the last few years electronics have started to take over from steam driven instrumentation and the 737max etc shows how succesfull that has been.
I think we are going to have to differ on this one Chug, I rebuild and repair metal construction aircraft all the time BTW. You are just going to hate the idea of this then
https://www.junkers-f13.com/junkers-f13-relaunch-e