It depends. I bought my house on my own 3 years ago at the age of 27. two bed semi detached in good condition in a UK capital city (not London), without the help of parents, and up until then I'd never earned more than £21k (earn more now).
In order to do this I made a lot of cutbacks/choices which some people of my age weren't/wouldn't be prepared to do, i.e. didn't get my own car for as long as possible and when I did it was third/fourth hand, lived in crappy houseshares, worked part time consistently through school and uni, never bought designer or even expensive high street clothes, etc.
I didn't completely abandon all fun though, I still went on a good few holidays, went out drinking, for meals, to gigs etc. But just didn't go crazy on the luxuries like some of my friends did.
However I don't want to go full on 'if millennials stoped eating avocados....' I fully acknowledge that I benefited in some ways that others may not have the opportunity to, i.e. I saved a lot of money by living at home at a low rent for a few years after uni, had the (physical and mental) health to work, was lucky in that my job and family were within an affordable area of the UK so I didn't have to move miles to afford to buy, etc.
So YABU in that it is technically possible, but it's not easy. And for some people the compromises it would take (whether than be moving far from family or giving up expensive holidays) aren't worth it for them. Which is fair enough. I'm really glad I own my house and wouldn't have changed my choices, but don't judge anyone else for not owning.