Orbital Sciences Antares rocket uses previously mothballed Russian NK-33 engines. These were originally manufactured for the Russian version of the Apollo program but never flown. These are 70's vintage engines that get refurbished and launched. Also notable they are closed cycle engines, which was seen as somewhat impossible to achieve at the time. SpaceX newest engine uses the same concept, probably inspired by these engines.

Documentary about this on Netflix

https://www.netflix.com/title/80119093

I think the documentary makes some great points about how limitations drive creative solutions.

That was actually his plan in the early days of SpaceX. But the missiles were too expensive, so they started from scratch.

But a lot of commercial launchers are incremental improvements on old designs. The Delta family is based on the Thor ICBM.

Soyuz was first launched in 1966, and it's the only way to get humans to the ISS at the moment.