Our cruise (we are Dutch) with the Marco Polo was not too bad taking into account some negative reviews on this site.
The ship is old and that shows. During our trips there was a lot of repairing and painting going on, restricting the available space on the decks.
The itinerary is interesting but remember the Amazon is very wide so the panorama is rather boring and there are many seadays.
The crew is mainly eastern european. They are in general friendly and kind but not too service orientated.
Ours cruise started with the aftermath of a Noro virus and halfway there was a full power breakdown luckily on the Amazone and not on a rough open sea. The
failure was blamed on incoming rainwater and that is rather alarming.
The food was good, sometimes very good.
The showteam was excellent.
The atmosphere among the travellers was fine
Public space limited
Cabaret old fashioned
Prices and quantity of drinks
Dinner time available
Coffee very poor, buckets of boiled water added
Smoking policy very liberal and no effective control
Very loud music everywhere, good if you do not like to communicate
Port information insufficient
Poor isolation of cabins, you can hear your neighbours talking
Lots of noise from the waves
Poor view from the interior
Decks are not cleaned sufficiently
Excursions expensive, few transfers and costly if provided