You need to ask the right questions of the hotel in the first place.
We have been using the Marelen since 2001 and, like many other Zante hotels, it's excellent.
They have built a ramp up to reception for wheelchair users, so that's great newsl. But from there you can have access to their minimal "supermarket/cupboard"
But it's steps up to the breakfast buffet area, also to the bar and lots of steps down to the public loos.
As for access to the eating/restaurant areas from the outside/poolside, there are 3 or 4 tables at ground level, next to the pool bar, but the main eating area is up steps.
There are some ground floor rooms that are accessible from the flat paths, but many require using steps. That's right, steps to a ground floor room!
So, to precy, a hotel can have wheelchair access to the reception, poolside, pool bar/cafe and limited tables, some rooms/apartments, but you could be excluded from the main bar/lounge, main restaurant areas and have a very limited choice of rooms.
You really need to ask the right questions directly to the hotel, preferably in writing/email and any ambiguous answers would need to be clarified.