Success is almost always a combination of both. No one is self-made but that tends to irk people who believe they are because they've spent years doing a lot of hard work. Without that hard work they'd have failed! Yet hard work alone is not sufficient.

Where you grow up, what schools you attend, who your childhood friend group is, luckily not getting hit by a bus and put in the hospital, etc. A whole host of factors conspire to grant or deny you opportunities.

However once the opportunity arises you have to seize it. Many people have lots of opportunity yet accomplish nothing because they lack the skills, will, or both to do so. Conversely many people with the drive and skills never hit the right opportunity and end up nowhere.

For whatever reason the broader culture seems to bounce back and forth between both extremes. The whole "pull yourself up by your bootstraps" and "get a job you lazy bum" crowd acting as if you can get rich purely with hard work. Then on the other side there seems to be this well-intentioned idea on the left that if we simply give every under-privileged kid opportunity they'll be successful.

Real humans and real lives are far more complex than such simple notions.