Most posters agree a move or transaction is worth it, if it produces a world championship. So was the Kimbrel trade worth it? It directly played a large role in three straight first place finishes, including the 2018 ring for the best Red Sox team of all-time. Kimbrel almost gave me a heart attack in the '18 postseason, but he was mostly a stabilizing force that solidified the Sox into a contender. He also saved over 100 games, was a Boston All-Star from '16-18, and even finished 6th in the Cy Young in '17 (Sale was 2nd).
Margot, the best of the prospects swapped for Kimbrel, has been an ok big leaguer. This is nothing like the 1987 deadline deal that brought starter Doyle Alexander to the Detroit Tigers. For the last two months of that season Alexander was the best pitcher in baseball, going 9-0 with the lowest ERA and WHIP. His addition was totally worth giving up prospects at the time because it made the Tigers the winningest club in the majors, and the favorite to go all the way.
Then Alexander lost two playoff starts and Detroit didn't even make the World Series. Meanwhile, one of the prospects eventually did better than just ok for his new team in Atlanta, and even became a famous TV analyst on FOX...