Why would you want the quality of a team to influence a statistic meant to evaluate a single player, though? That's why win-loss record for pitchers is irrelevant now a days. It's too heavily dependent on how the offense and bullpen did. It's not good for evaluating a player.
If the White Sox win 90+ without Eloy and Robert, it means the team was really fricken good. It means they'd be even more dominant with those guys.
WAR is wins above replacement. It calculates how much better a given player is than a replacement level player in that season. Team success has little to no influence on it.