The bottom line is he's untradable with the contract he has. You're right that they wouldn't have to pay 70% of his contract if they got back a worse contract.
It should have happened last off-season when his trade value was sky high. He still has decent trade value, but it will probably decrease because he is labeled a utility player. The Cubs should have traded players like Wicks and Alcantara while they still had some trade value.
Earlier you said that players typically play to the back of their baseball card, Contreras has .817 Slug, and OPS+ of 120, and an AVG WAR of 4.5 over 11 years. He is outhitting those numbers this year, but you could still count on him adding a lot to this lineup everyday.
I don't know about the highlighted part. Putting a batter in the everyday lineup who has a .918 slug and an OPS of 160 and is on his way to a 6 WAR could go a long way in covering some of the black holes and slumps.
It sure isn't the game that we grew up with. Mediocrity has overtaken stars - batters who hit .240 that strikeout twice a game are considered stars because they hit 25 HRS and pitchers who throw 5 innings per start are considered Cy Young candidates.
Don't forget the pitching staff of Boyd, Imanaga, Taillon, Horton, Palencia, Keller, Thielbar, and Pomeranz, some of whom had career years while the rest had very solid numbers.