Iflyplanes. Your comparison between a brand new BMW and a clapped out Morris Minor is incorrect.
When you buy a new aircraft, you are also buying the teething problems and hidden defects that come with it, as the owners of BMW 7 Series cars with software problems will tell you.
It may be news to you, but Airbus and Boeing go to very great lengths to make sure that everything that can be replaced or rebuilt in an aircraft, can be returned to original condition.
The bits that cannot be replaced or rebuilt easily, like the wing center section, are built not to fail within the likely life of the aircraft, like the chassis of your hypothetical car.
Furthermore, my guess would be that when your bright shiny new aircraft arrives from the factory, the first thing maintenance will do is take out at least one of those bright shiny new engines and chuck an old "Clapped out" (your term, not mine) engine on the wing in order to equalise things in its engine module maintenance schedule.
Furthermore, the tires, wheels and brake packs you run will be similarly "clapped out".
Please do not confuse bright shiny aircraft interiors and cockpits with increased safety. There is little if any connection provided maintenance is first class.