Reality check
Given all of the unknowns, the only reasonable bit of conjecture here is that the aircraft (whatever it was) may have been operating too heavy and thus very close to performance limits.
Technological developments to reduce helo noise signatures, a big YES; but low observability and stealth would really be of very dubious merit, bearing in mind what helos are supposed to do down among the weeds. Cost also comes into play; for example, Huey II - $2million, UH-60M - $20million, NFH90 - maybe somewhere between $45-80million. Maintenance/operating costs also go up exponentially for composite LO hardware.
Most nations will be forced to operate helo types that are affordable and readily available for special operations work and not the super-expensive James Bond style stuff.