Arguable Tommy Armstrong did improve his quarterbacking under Riley/Langs as he did cut substantially his interceptions and in that way his decision making (the area most needing improvement in my view). Many 'experts' tried mightily to get him to improve his footwork and other basic QB physical skills and to improve his reading of defenses, finding open receivers, etc.
One could also make a case that Tommy may well have improved his footwork techniques except for the fact that he rarely had sufficient time to really properly set his feet and throw the ball in the ideal form as he was usually running for his life and could not count on the O line giving him sufficient time to carry out his responsibilities timely.