Tricky. There are a lot of different issues in your list, which probably require different ways of tackling them. And tbh not many of them fall directly under the ‘care’ label - some are ‘life admin’, some are not urgent (many people live in messy houses with ood did in the fridge, others are probably more urgent.
so for me, I would try and deal with the issues seperately and in order of urgency.
top priority has to be safety: how safely can they live in their house and how can it be made safer? Have they ever had a care assessment? Has your mum been assessed for her memory loss? Or your dad for his frailty ? Does he struggle in the house? That’s not imposing help on them - it’s making an objective assessment of whether they need help and what kind. your dad taking his medication correctly is part of this, it’s personal care and living safely.
second for me would be your dads driving. how serious are you when you say he should not be? This is one that would keep me awake at night. Does he have any medical conditions that should be disclosed to the DVLA? How much do they rely on driving for transport? Is he having small accidents?
for the house stuff, like I say a lot of people do live like this. How do they feel about you tidying / filing / rearranging / declutterring / taking on admin for them? Do they recognise that it’s an issue? The way DH and SIL tackled this was for DH to basically get into everything - bank account reviews to work out what he was spending on (there were lots of old subscriptions and direct debits still going out, he was paying for two phone subscriptions etc), filing years of paperwork and setting up a new filing system for FIL. Also decluttering the house, removing rugs / stools etc, and getting handrails etc put in. Also set up a taxi account, as we had to take his keys / car off him.
But tbh the whole thing depends on SIL popping in 2-3 times a week to check the mail, deal with admin, remind him about any medical rdv and take him to them, check the fridge for ood food, stick a wash on and just generally keep an eye on things. He also has carers going in three times a day, but they don’t do any of the above. Do you have any other siblings or anyone able to pop in?