I don't believe they are "cheapening" the cars. The goal is to attract the younger buyer with lower priced vehicles like the C and the GLK.
After you have disassembled parts of a 2000 S500, 2000 E55, 98 CLK320 and other of the 1997-2005 AND a bunch of 90-95 560SELs, S500, 500Es, 300Es, SECs and cars of that era you will understand what cheapening occurred.
And some of the parts that I have always watched for quality [like the little window lift switches] continue to be much cheaper in quality/performance than their predecessors. If you can't get a window button correct...