Its a fair point. Here's a chart I made chronicling the last two seasons from the three goalies who've played regularly in both of the last two seasons at KHL powerhouses, SKA and CSKA. The first number is save percentage over the two years. The numbers in the parentheses are games played, and shots faced per game. Player 1 is Shestyorkin, player two is Koskinen, player three is Sorokin.
1518/1623=.9353 (67, 24.22)
1195/1288=.9278 (52, 24.77)
1573/1692=.9296 (76, 22.26)
The best stats of that bunch are player 1, so its not like he lags behind others on the powerhouse teams. The shots he faces per game are lower than the NHL, but its not like SKA faces 10 shots per game. SKA faces around 4 shots per game less than the NHL leader most seasons. And while SKA is a powerhouse, they give up a lot of odd-man rushes. They are not as good defensively as offensively. I should also mention that he has played games where his team sucked, and he had to drag them to a win. When he was playing in the VHL, his team was awful, and he nearly dragged them to the Championship putting up the best stats in the league's history. He dragged Russia to the WJC finals in 2015.