I actually thought this was a good trade back in the day based on the way he was pitching, but the injury happened and basically nullified it. There weren't any red flags medically that we were aware of, so unlike some other pitchers they have traded for and immediately got hurt, I think this was plan old bad luck. Then that controversy came out and that was the end for him.
Part of the dislike of the trade came from trading Jaylin Davis, who was killing it at AAA but in reality was a AAAA player and proved that. His 2019 season at AAA was bonkers, hitting .300, 35 HRs and just short of 1.000 OPS. Teng and Berroa have pitched in 2024 in the majors but are fringe guys, and were seen as mere lottery tickets at the point of the trade.