I reluctantly agree that an animal isn't a basic need that must be met, and reluctantly because I have had periods in my life where I've been desperately lonely and my dog and the horse I looked after (expenses paid) were the only things that stopped me sliding further into my own head and developing unhealthy habits.
This was a two way street though, they have shelter, security, warmth, comfort, food, water and veterinary care when needed. They are kept free from worms and fleas and groomed to ensure they're healthy. They need to be walked because they don't live outside with the ability to roam free and therefore need exercise and stimulating, this helps me as well.
It's a relationship that's mutually beneficial. I know legally I 'own' my dogs, however I don't think of them like that, I think of them as dogs, because that's what they are, but also as other sentient beings that I have a mutually beneficial relationship with.
I do agree with your point about the advancements in veterinary care and that vets were for 'major' things, not cuts and scrapes or an upset tummy for a couple of days. I don't think it's necessarily a bad thing for the advancements to be available for those who want it, but I do think it's unreasonable to expect everyone will subscribe to this and to accuse people of being irresponsible if they don't immediately rush off to the vet and spend a few hundred on something that you could treat at home effectively, or that would heal naturally on it's own without any intervention. Or if someone chooses to have the animal PTS over chemo and surgery with a cancer - I have worked with people who are undergoing chemo and it's hard enough for a human that understands, I wouldn't be doing it for any animal, regardless of cost because I don't think it's fair. I'd opt for pain management for as long as possible and then PTS when quality of life deteriorated. I wouldn't judge anyone for doing it, it's up to them, but I also wouldn't expect to be accused of being an irresponsible owner because I didn't choose to pull out all the stops to save the animal. I truly believe there's worse than things than being euthanised for an animal, and animals aren't sentimental, we as humans bring that to the relationship.
Of course I'm not advocating for animals to be left in pain, bleeding or injured, but as you say, people generally don't go to the Dr for every little bump, scrape and people do opt for no treatment to extend life in the case of cancer or other life limiting illnesses.
I do think that you should be able to provide basic care, food, water, shelter, warmth, parasite control and grooming (even if this isn't done professionally, I bathe and trim my own dogs when needed) and veterinary care, even if that's basic so pain relief measures/emergency or euthanisia.
I have basic insurance to this end, can afford the basic needs, but wouldn't be persuing invasive or aggressive treatment even if money weren't an issue.