My husband and I have visited several Greek islands over the last few years (some more than once) and have absolutely loved every one of them. They include Crete, Kos, Rhodes, Kephalonia, Zakynthos, Ithaca and Thassos. We have just returned from Kos and already have next year's booked to Alonyssos. It's true that Greek standards are different from UK standards but we have always found the accommodation to be clean with maid service on a regular basis. More basic than luxurious. We prefer to stay in self catering apartments rather than tie ourselves to only eating at a hotel. I love Greek food and enjoy Stifado, Kleftico, Souvlaki, Moussaka, Greek salads and if you are a garlic lover, then you must track down Skordalia. Heaven!
Don't be put off because there are many wonderful places out there. Greek people are amongst the friendliest on the planet. For example, after a boating accident where both my husband and myself were injured, my husband's wallet was lost overboard. The hire people were not a jot concerned about their boat being damaged but were most solicitous regarding us. They took us back to our apartment, contacted a doctor, offered to lend us money and returned each day to take us out and about. I must add that the accident was not down to the boat being faulty but us misreading the currents.
Go for it. It's a whole new experience.