"In my day, forgetfulness and confusion was just old age, now everything is labelled as dementia"

Mobility issues and unsteadiness in themselves can be a sign of vascular dementia - along with memory issues. Would suggest visiting a GP. There are treatments to help alleviate symptoms and delay onset of the worst ones. Being in denial really doesn't help with some forms of dementia.

A certain amount of forgetfulness was viewed part of old age, and probably is still part of a natural slowing down. Dementia and Alzheimer's are beyond natural old age forgetfulness.

People live much longer today than when the current generation of 80+ year olds were in middle adulthood. With people dying younger, the sort of long, slow decline some people experience these days is probably something that some older people didn't see very much when they were younger. It might affect how willing some of them are to accept that dementia is something that could affect them and/or their spouse.

Not necessarily wrong. Of course it should be checked though.

Does your dad need more support than he already has? If he needs support / moving to a care home even, and you feel that your mum won't do this because she doesn't (can't / won't) accept it then one option is to contact adult social services, say that your dad has dementia, and that your mum is refusing to accept this. You can also contact their GP and while they can't discuss anything with you, you can tell them your concerns and they might invite him / her in for a 'check' and see if they can pick up on any concerns.

Ime - I let it continue until my parent was at risk of hurting themselves then contacted adult social services. My parent wouldn't cooperate with assessment so they were sectioned in the end and now, 3 years later, they're in a much much better place, mentally and literally. They haven't significantly declined any further, they're quite content in their care home (we were very lucky) and the 'in denial' parent is ok. Not thriving, because their role had become The Carer and they struggle with a loss of identity.

I don't necessarily disagree with that statement though, those are traits of old age. Of course there can be dementia, but not always.

Whether your dad has it though will need to be determined through checks at the memory clinic.

Has he got a diagnosis of dementia?

Has he or would he agree to go to the GP?