Both Cano and Diaz have been disappointments, although they have had some good moments, too. Cano played 156 games for the Mets and hit .275 with 37 doubles and 23 home runs, better numbers than people realize. he's suspended for the 2021 season. I haven't found anything saying that he couldn't be a Met in 2022, so he may not be done. Diaz has blown 11 saves but made 35 of them. He's not done.
Jay Bruce played 47 games for the Mariners, batting .212 and moved on to the Phillies and Yankees and has announced his retirement. Anthony Swarzak pitched 15 games for Seattle, going 2-2 with 3 blown saves. He went onto the braves, the D-Backs and signed a minor league contract with the Phillies. Gerson Bautista pitched in 8 games, a total of 9 innings in 2019 with an 0-1 record for Seattle in 2019 and hasn't bene in the majors since. Justin Dunn has done pretty well in limited action for the Mariners, starting 18 games with a 5-1 record despite a 4.04 ERA. The key player for Seattle was Jarred Kelenic, who has done well in the minors, hitting .273 with 29 homers and 35 steals in 173 games. people who say it was a lousy deal for the Mets are primarily talking about him. But he has yet to play a major league game yet.
Trade sending Robinson Cano, Edwin Diaz to New York Mets from Seattle Mariners now official (espn.com)
This may someday become a bad trade but so far the Mets have gotten more out of it than Seattle has.