I would tend to agree. Maybe if you came across some ‘craft’ that was 100 years more advanced...you could backwards re-engineer it (figure 10 to 20 years).
Beyond that? Say a craft that was 1,000 years more advanced? Then you say that you can only have five to ten engineers with massive secrecy involved? You could waste 40 years and have minimum to show for the effort.
The bulk of this whole story is not believable. The rest of it...suggesting massive alien visitations? I’m still waiting for more evidence. Meanwhile, I’m wondering...wouldn’t the Russians and Chinese have their own programs?
Yup. The Russian one works 25% of the time. Chinese is smaller and you want more in an hour.
Chances are high that the craft was 1000 years in advance of anything we have 12,900 years ago because they are part of one of the previous civilizations that existed prior to the catastrophic comet debris that fell for 100 years over all of North America, much of Europe, northern Africa, and a lot of South America.
4% of the world’s vegetation as burnt off and resides now in a geological layer called Black Mat. The Earth likely lost a good percent of its oxygen as well due to the raging firestorms.