If tic-tac style tech / anti grav is readily available to us and has been reverse-engineered, why invest billions in traditional jet power super fighters?

As per the title. Is it to further hide the real available tech, ensuring that we never reveal the extent of the tech available?

Or is it that these fighters actually utilize NHI tech and we just don’t know?

I refer to fighters such as the following: https://en.wikipedia.org/wiki/Northrop_Grumman_X-47B

These cost billions to research and each one costs at least a million to produce.

But the propulsion utilises standard, modern jet tech.

What are everyone’s thoughts on why future fighters aren’t more like what we’re seeing being reported by military reports such as tic tac, etc?