I might suggest he may never improve on his completion %. With vastly improved coaching, offensive line, and skill players, and after playing 25 games in the NFL, his completion percentage is lower this year than last. However, not all HOF quarterbacks had great accuracy. Brady was at 64.3% for his career, but then again, he is arguably the GOAT.
The following list was from a Google AI search. I did some spot checks of the figures, and they seem accurate. Some rounding up or down, but very close or exactly as noted in online references for individual players.