Most all shooting percentages hover around that area, it takes alot of shots to alter a field goal percentage, specifically for a top ten scorer. He went from an above average perimeter scoring percentage to a mediocre one. He took 300 more shots year over year while missing 174 more and scoring less a game. He took 100 more threes If you ask me, he became an even dumber player. You can argue that he somehow didn't regress but please spare me the he got better shit.
You ask a top 10 scorer to step into a bigger role and there shouldn't be a regression in the slightest, especially for a player whose "career is on the rise". For wade to be as over the hill as you say and Russel to be as good, there should be no reason for this to even be a discussion, yet here we are with you throwing convenient excuses.