To me, good ergonomics on a rifle mean that I can operate the rifle while expending the least amount of time and energy possible.
I think the M16 FOW got almost everything right.
The one change that I would like to have to the ergonomics of the AR is the ability to lock the bolt open with the same finger as I drop the magazine with.
So that if needed, I could lock the bolt open while drawing the bolt back with my off hand instead of having to drop the rifle down and use my right hand to draw back the bolt while engaging the bolt catch if needed for malfunction clearances.
Otherwise, it is superior to every rifle of it's time period and is the basis for basically all the newer generation rifles. (Same safety, mag release, bolt release)
While it is very possible to adapt to a gun with inferior ergonomics and that should not be a persons only reason for using a gun, superior ergonomics will always makes someone faster and more repeatable. (There are whole engineering disciplines built around shaving seconds and fractions of seconds off of operations by improving operator ergonomics.)
I am no longer participating in gun forums.