I think you are being a little harsh As a berth holder (for only two more weeks before we move on to Croatia) I will comment as below
Re land fill - must agree with you, as you sail down the canal it isnt a pretty sight, in summer the smell is pretty bad and as you say god knows what floats upstream into the marina. As for sewage smell, as Jim says, thats Greece Im afraid! It is actually worse on the town quay than in the marina but is typical of many Greek harbours that Ive been to.
Re fuel spills I'm not there at present so cant really comment but to be fair to the the marina, the guys on the fuel pontoon are on the ball re spills. I have a breather on my boat which unfortunately lets out a burp of fuel if the tank is filled too quickly. When this happened recently the fuel guys immediately sprayed detergent on what was a small spill. Ive also seen them practising fuel spill procedures with booms, fire tenders etc. I cant imagine that the fuel dock is the source. It could even be the seaplane - It comes right into the marina and leaves a fair old stink of aviation fuel in the air - it doesnt appear to leak fuel though or Id have been long gone by now!!
Incidently I saw a big "slick" when in Nidri last time so maybee someone has worked their way north with a leak!
Agree lots of concrete - can make it a little soulless at times. Toilets and showers are variable but the nearest one to my boat is approx 30metres away -
Cant disagree with your environmental comments but it sounds like you were unlucky with the rest.
Hope you enjoy the rest of the Ionian - we have over the past few years