re: Per capita, Louisiana is producing the most NFL skill/speed talent, and by a large margin

No, per capita is a valid measurement. Most Statistical analysis is done that way. Your point about Florida retirees and population growth their does not mean that population growth is limited to just retirees. So using population to scale it tells me something about how football is valued in a state.

I did not say it was the only way to measure it, standardizing by Football participation rates is good as well but it also has limitations. But Participation rates also have problems as participation rates vary across States and thus reflect a self-selection problem. So the ratios of State A vs. B reflect a Self-selection problem where Population rates do not. Population as the scaler does not reflect self-selection bias as much as HS participation rates, although yes people can move to State A vs. State B.

Still the ratio of NFL talent in Numerator to total population (Denominator) is not a bad measure.