Well yes it's unrealistic.
It was 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 the contrast between this imagined world - no matter how realistic or not - and the reality we actually got.