Very often people just confuse staying at a hotel vs staying at an apartment. I could read numerous complaints, on the totally normal practices at rental apartments. It is very normal to expect a clean rental.
However, for the rest of the details you have to read very carefully the description of all terms and of what is included. You also want to read reviews and consult travel forums when in doubt. If you doubt is big, save yourself problems and just look for another rental.
Examples of complaints:
No food at all left such as salt, coffee, oil or other: This is perfectly normal for many rentals. I talked to the owners and they said people complained if food remained from previous vacationers.
Food leftovers: many people don't like having food left, and therefore complain, so the owners simply remove it. Although we had been to rentals where the owners kept salt, pepper, coffee, dried pasta... and for us it was fine too.
No shower carpet, no soap, shampoo. This is perfectly normal, and you are expected to bring your own. Since there is no laundry service, unless you rent linens, it is normal not having shower carpet. Renting linens costs a fortune in Europe, for this reason I bring my own linens. It is possible to purchase cheap and lightweight linens and towels in North America. Otherwise you can buy it locally, however, they could be expensive.
No dish soap, no kitchen sponge or tea towels. Normal again and you should bring yours. Places with dishwasher usually had some. You also should bring your own soap for washing clothing, although some rentals had it.
No paper towels, no toilet paper. Normal, and you should buy it. Some owners and agencies are nice enough to have just some for you arrival.
No washcloth: this is normal anywhere outside of North American hotels. So you should bring yours if you need one. In any case you should bring your toiletries.
Some rentals may have umbrella and beach chars but other don't. Those that have it are usually left items from previous vacationer.
In general, many items are not at all an obligation to provide by the owner, but there are well organized and nice owners who have their apartments well equipped. One of our rentals missed a spatula, so I had to learn to remove fried eggs with two big spoons.
Examples of great surprises:
Our apartment in Cassis had a fantastic port, sea and rock view, but the original listing didn't show any pictures of this beautiful view, just mentioned a sea view. So, it was a big wow!
The owner of the apartment came to pick us up from the train.
Renting from homeowners directly in Italy and France we had a bottle of wine and home made jam left in one case and a bottle of good olive oil in the other as a welcome gift.
When we traveled to Rome with a toddler, the owner bought him juice and milk, and walked us all around the street and introduced us to several places, so we could order from them food for our 30 months old. He also provided such nice linens for the child. In general in Italy people were just so kind to the child and the parents. This was very touching.
In Sicily a man in our little building gave our son a little car.
French were also kind to our son. He received gifts even from people selling souvenirs.
At deluxe campsites we received a cleaning welcome package with toilet paper, soap and sponges.