I commend that you'll wait to see how all parties involved turn out but from the very start that trade looked lopsided.
Fedde had proven the changes he made in Korea were legit .He has a solid big strong body, and ptched extremely well for the Sox and had the extra year of control. Vargas was on a downward spiral with the Dodgers .He could put up great AAA numbers but he had no position to play and had yet to figure out MLB pitching.
Fedde may very well be a 5 WAR starting pitcher for the Cards next year. All he has to do is have a 2025 as good ashis 2024. At the time of the trade he was more valuale to the Cards than Tommy Edman was who hadn't played all year.
No one's pretending Kopech is a Cy Young finalist but as far as I know the Dodgers did nothing to fix him unless someone can find something specific that I couldn't.
The fact is in his last 5 appearances with the Sox he pitched 5.2 innings 0 R, 1 hit 1BB and 8K after he finally started to trust his coaches.
He just continued doing with the Dodgers what he had with the Sox .
24 G, 24 IP, 9 H ,3 ER, 29 K, 10 BB 1.13 ERA , 4-0 Record, 6 Saves , .792 WHIP and thats with a walk rate of 3.8 per 9 IP which is still a bit too high.
But over his last 29.2 innings he may have been the most valuable RP in baseball.
It's not like he had lost his stuff but he had lost his way. He was stuck between the pitcher he wanted to be and the pitcher he could be and it took him a while to trust a lesser vision of himself in his mind and accept his new role as a RP and how best to approach that role. The Dodgers were 19 -5 in games that Kopech pitched.
Someone of the 3 guys the Sox got has to become a productive MLB player. It would be nice if it was Vargas but he couldn't have been any worse than he was with the Sox with a -1.0 bWAR in 42 games. Kopech gave the Dodgers 1.0 bWAR in his 24 games and and a dominant late innings presence.
The trade from the very beginning felt 1decent prospect short or a better headliner short. We got something you might be able to squint at and eek out a MLB player somewhere down the road for productive MLB talent.