I think whether you need to clean or not has a lot to do with the breed of dog and what its ears are like. I am sure that in theory no dog should need its ears cleaned as nature does have an efficient self cleaning mechanism for ears but the reality is that some concentrated inbreeding has resulted in some breeds having ears that do need help with cleaning. The obvious ones are those with floppy ears but there can also be a problem with some breeds that have lots of dense fur.
I think the best thing to do is see your vet and be led by them - they will know if any help is needed and tell you how to do it.