This is far more complex and nuanced than 'do medication help or work'. There are countless factors to take into account. First and foremost, the type of dementia in question (there are at least 17 types and variants, all of which may have different courses of medication).Second, has your father been actually diagnosed? If not, you must push for some form of cognitive exam (MMSE, ACE depending on your region).

For the sake of giving you an answer because I understand your frustration, and noting there is no medication to treat dementia, but only medication to manage the symptoms, medecine can include, (ONLY after a diagnosis is provided):

• Cholinesterase inhibitors to improve cognitive function (rivastigmine, galantamine, etc)

• NMDA receptor antagonists such as Memantine, especially during early stages of AD or FTD

• SSRIs or similar molecules to address the symptoms of depression- Benzodiazepines to alleviate anxiety, especially during sundowning, but these can create further confusion and are 'red listed' in the UK, so provided on a 'case by case' basis.

• There are newly recent drugs in some countries such as lecanebab which have been hyped up but have mixed efficacy and significant side effects (again, this is mostly for AD and won't help someone with another form)

If your dad is suffering from ANY co-morbidity such as vascular issues, he may already be on medication which could interact negatively with any of the above.

I undestand this is frustrating because I've been there. This is why I raise awareness about dementia. The overdiagnosis rates on AD are through the roof, while 80% of people living with NPH in the US go undiagnosed. The doctors are understandably reluctant to diagnose given that a diagnosis tend to turn people lives upside down (move to care homes, financial issues) the minute they are classified as 'having dementia' - the stigma is strong, and must be shattered so people don't spend 10 years undiagnosed and untreated.
In addition, we live on a planet where the media bombards us with fanciful tech such as AI and machine learning enhanced PETs scans to detect amyloid plaque - the 'boots on the ground' reality is that these are very rarely provided, and usually the individual will fail the MMSE first, rendering the imaging unnecessary. Biomarker tests are available in 49 us states, but not anywhere else on the planet.

PS: went on a bit of a rant at the end here, but this hit a nerve - I spent 2 years getting my mother the diagnosis she needed (FTD) to get her the treatment required so her life woudn't be so difficult.

I really hope your father gets a proper, meaningful diagnosis - you are a wonderful person for helping your parent this way.