You must specify the season() option to remove duplicate names for each year. For example, to use this years stats you would type:
nfl2stata player quarterback, season(2018) seasontype(reg) clear
graph bar (asis) yards if yards > 500, exclude0 ///
over(name, sort(yards) descending label(angle(forty_five) labsize(small))) ///
blabel(bar) title(2018 Passing Yard Leaders)