I feel your pain, we where on Mariner April 22, dining waits in MDR for my time were bad. Fit and finish poor, lots of rust around windows, water stained awnings and flaking woodwork in solarium, mis matched fittings in public restrooms.
I feel that the America based lines (no offence, I'll include NCL in this too) don't keep up the maintenance schedule that we have experienced on other european lines such as Costa or MSC on ships of a similar age or older.
We are pretty easily pleased and Mariner was only our second diamond tier sailing, previous being Jewel pre covid transatlantic, which we loved. The four "happy hour" drinks do go someway towards levelling the field.
We're on Jewel again this September, in Europe, hoping for the best.