I am just back from a cruise on the Ryndam and from what I saw, only 5% of the passengers followed the dress code. Not that I am complaining!
Jeans were almost mandatory - I felt overdressed and I never anticipated that!
Also why would anyone want to dress up to eat in a manic MDR with poor food and poor service is beyond me!
I and several others only ate in the Pinnacle or the Canaletto. As a consequence, it was very difficult to obtain a reservation in these alternatives to the MDR.