He was +2.7 last year and this year is barely negative due to defensive stats that vary considerably. Not saying he is an All Star, but I believe he is a legit MLB starting catcher and we did mostly develop him.
The whole discussion is about why we did not keep him - and that is because we played JT almost every day and the potential benefit of getting Marsh outweighed the value of what we saw as a catcher who would not play that much.
Now who won the trade? Only time will tell. The WAR of Marsh has been better, though situationally helped by not playing much against LHP and also playing more LF (where he is positive defensively) than CF (where he is negative). Marsh also is a negative WAR player this season just like O'Hoppe and he still is helped in that stat by not playing much against LHP.