They must have made some changes as my 2018 fit and finish is great. Car rides like a dream in the comfort mode and acts like a sports car in the Sport+ mode with the higher shift points.
I'm just having a ball driving this car.
Just my $.02 worth.
I think MB got lot of feedback on the 2015 C300s, that they had to impove. I have not driven the 2018 models, but it is too late. I have lost confidence in MB.