Why Can't we Remake the Rocketdyne F1 Engine?

Technical know how, mostly. But in expected ways. Machining and engineering skills as they relate to manufacturing are different now. ▶ this video

Sure. Not a source but still interesting. ▶ this video (Why Can't we Remake the Rocketdyne F1 Engine?) TLDR: everything was handcrafted, notes were not made or lost, people have retired or passed away and today's engineers don't know the tricks that the original engineers used. Effectively, existing blueprints are not enough to rebuild the engine.

You'd have to redesign it from scratch - it would be faster. Which is what happened with the SLS engine/launch vehicle. Duplicating the F1 would involve technology and knowledge of individual engineers who are dead and corporations that no longer exist. The TACIT knowledge and technologies required to go with the blueprints died with them. link link ▶ this video

Reminds me of how NASA had to design completely new rocket engines for SLS because while they still had the plans for the Saturn-V rocket engines, back then plans weren't followed to such high accuracy as nowadays a 3D model would be followed. Each engine was custom tailored with small modifications here and there. The knowledge to custom tailor them was lost, so they went with designing new engines from scratch instead. ▶ this video

Yup that's what curious droid's video on this is saying as well [1]. Basically the plans all were off a little bit and each rocket engine was hand-tailored to the demands of the individual rocket by these skilled people you mentioned. They did document their changes but only on scrap notes that since were lost. The plans themselves that were archived don't contain those notes and even if they had them, you couldn't find people with such skills any more. [1]: ▶ this video