Well, lottery and inheritances excepted, you won't become one if you don't work hard.
The main problem here is that much of US society believes it is a necessary and sufficient condition - i.e., they've perverted "you need to work hard to get rich" to "if you work hard you will get rich", or the more pernicious format: "if you're not rich you didn't work hard".
The last form of this thought is one of the most persistently toxic concepts of modern US society.
I don't know of people in the UK that can get into universities with significantly lower grades, just because of their family.
And the part about jobs migt be true for a family firm, but I doubt if it would work at, say, IBM.
Yup, my fault, not clear enough. I'm talking about the US more than the UK, although now that UK universities have essentially been told by the government to behave like businesses, with poor people already less likely to apply than the rich since fees went from zero to almost ten grand a year in the course of a decade, I expect the UK to catch up soon enough in terms of buying your way into a good university (there is indeed already rumbling about places going to foreign students who can be charged far more than home students, establishing the principle, so I expect that as soon as universities work out a way to let people buy their way in, they will).
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Edit to answer this point below: ""Give up, no point working hard, you will never make anything of yourself, the game is rigged"?"
No. My alternative narrative is "know the game is rigged". If you're playing a rigged game, your chances are so much better if you realise this (hence my very first post here - the people who rig the game work hard to make the unlucky ones think it isn't rigged).
"Some people will have it much, much easier than you and some people will have it much, much harder. That is irrelevant to how well you do, so have at it."
But going to the right school makes it considerably easier to go to the right University in the UK and going to the right school really is very strongly tied to wealth and status of families.
Case in point: categorical prioritization of progeny, inherited wealth, or the impact of power and wealth acquisition on the functioning of an otherwise more productive mind.
(ETA) Part of the reason we, as software engineers, don't have a lot of autonomy or respect is that we don't have the tribal mentality. Many engineers will gladly sell out their own colleagues to management in the hope of getting a promotion.
So yes, you can continually get through on connections despite what we would call meager effort, at that social milieu. It won't make you CEO, but you can move fairly seamlessly from one high-prestige job to another.
Or that, like, junior lawyers at big law firms are these community-minded individuals who just pick up the slack so that their colleagues can coast?
A lot of people from my college went on to be lawyers and i-bankers. My understanding of those jobs does not match your description. Like, even a little bit.
There are undoubtedly people out there who are underqualified and coasting in cushy jobs that they got through their connections. But the finance and law jobs that super-elite universities feed into to a grossly disproportionate degree are -- at their junior levels, at least -- overwhelmingly not those jobs. They're high-paid, but they're both grind-houses and shark tanks. Their cultures are ones of shallow relationships, little loyalty, and burning out junior employees to support a pyramid structure of more comfortable senior people.