When the 1950s thought flying cars would be real they didn't mean military VTOLs or expensive and noisy helicopters.
They meant flying cars that are efficient, quiet and affordable. Flying cars that are so ubiquitous they are parked on every driveway in the country. Flying cars where you go to the showroom and test-fly one in your favourite colour, and it only costs as much as an SUV does today.
More importantly, it's not really the car itself that matters for the meme, it's the idea of the society that goes along with it. The imagined future where we have flying cars on every driveway is one where we also have robots doing all the menial labour, one of utopian prosperity, where everyone is educated, happy, and spends their days in fulfilment of personal pursuits.
That's what "flying cars" alludes to, and it's a long way from a society where people have to be warned not to eat a sandwich wrapper.
Well yes of course it's unrealistic, as we understand it today.
It's an imagined future based on boundless optimism that things would keep getting better and better, both technically and socially.
Inventions and discoveries at that time were happening so rapidly it surely felt like some revolutionary new thing was always just around the corner. We'd probably invent some amazing new levitation technology that would let things hover without making any sound, and it would all be powered by individual nuclear generators in every car, because why not right, nuclear is the future!
It was a dream from a time of optimism that never came to pass. The current day meme isn't about literal flying cars, it's about a hopeful world full of potential that didn't happen.