> That's like saying a Apple M2 Max is mundane because you've got a CPU from the 80s.
Yes, exactly. Give a modern Apple CPU to some chip experts in the 80s and they'd no doubt be amazed and have many questions about the details, but they would have a theoretical basis for understanding the premise of the thing. Give the same chip to Isaac Newton or Archimedes and it would be a completely different story. To them, a CPU would be truly exotic technology.
Antigrav existing today would be like CPUs existing in Newton's day. You'd need completely new theories to even comprehend the most basic operating principles. Antigrav craft like those proposed by the people who don't believe Mick West's explanation of the Navy's "Go Fast" video would be further removed on a theoretical basis from the F-35 than the F-35 is from the Wright flier.
> The few examples we know of were definitely cutting edge exotic technology at the time they were classified including the Manhattan project and the development of jet engines.
In both of these cases, the fundamental operating principles were widely known to relevant researchers in various countries before anybody developed one that worked. Japan and Germany both had nuclear weapons programs during WW2. Nuclear fission was known to researchers in all three nations, and more as well. In the case of jet engines, you had inventors in many countries taking stabs at implementing a practical one decades before they were adopted into military service. There was never a chance of any military getting jet engines while the rest of the world was left wondering what the hell it even was.
And with respect to gas centrifuges; those were considered but ultimately not employed by the Manhattan Project, which instead used gaseous diffusion. But the premise of gas centrifuges for isotope separation was first suggested in 1919, and the broader premise of any sort of centrifuge to separate things is much older. Gas centrifuges weren't exotic technology that game out of nowhere, the theoretical basis for them was clear before they were successfully created.