My inlaws for example. Fil doesn't think they clean properly. But that's because he can't /won't stack it using common sense. It's not like they have no experience of using one. Before they downsized to flat they had one in the family home. When they come to visit they will offer to clear up after we have cooked but we always end up having to unload it. I'd rather they didn't do it. Plates laid flat one on top of each other. Cutlery dumped in a massive bundle flat ontop of plates. Glasses turned on their side, bowls inside each other. I mean even if you didn't know exactly what each section was best suited for common sense would tell you that no matter how good a dishwasher you have it won't clean if the water can't get to it. I did try showing them how the racks separate the items so the water can flow but I honestly don't think they understand.
In the interest of fairness so you know that this isn't a inlaws bashing post I will explain that my mum has other similar problems with our dishwasher. Her top drawer fits her bowls, but our bowls are slightly too tall, as we have a cultery drawer above. Every time she tries to ram the bowls on the top shelf so that it jams.
She also has a habit of wanting to.wash up.a few items at a time to be helpful. Our dishwasher goes on every evening. We use enough stuff to warrant running it. if she wants to.do a job then the ironing pile is never ending! We don't own fine bone china or cut glass, everything is dishwasher proof, just stick it in. But she thinks it it's helpful to wash up. Except she won't use really hot water just tepid water and as we live in a hard water area it leaves all the pots with a greasy, scummy film on. So I have a half empty dishwasher that needs to go on so we have stuff clean for breakfast and a draining board full of stuff that needs to go in the dishwasher anyway.
Please add your tales.