I think that's more of a convenient excuse than the primary cause for that team not making the playoffs - Yelich had a bad year, the team in general couldn't hit, Peralta missed alot of time in the rotation due to injury, and at the time the trade happened, Hader was pitching terribly. All that being said, that team still wound up 10 games over 0.500. Hader was possibly the biggest reason the team was dropping in the standings after getting off to a 32-19 start to the year. Once the calendar hit June, the team basically muddled around 0.500 in large part to the inconsistent offense and leaky back end of the bullpen that got overworked due to starters wearing down/getting injured. Hader was on the roster when they went 3 games under 0.500 in June and hovered through mediocrity through most of July while he was sporting a 1.200+ OPS against and blowing saves. Hader's August in San Diego was equally as bad - had he remained a Brewer with that production they wouldn't have wound up just missing a wild card in 2022.