It's impossible to become rich without exploiting the labour of people poorer
By and large, I think that's true, but there are significant exceptions.
I always think that it's not having the money or enjoying/making use of it that's the problem - it's when you get to the point of worshiping it, obsessing over it, thinking it's the only mark of your (and by extension, everybody else's) worth or lack thereof - that's when it really becomes pointless.
By way of analogy, we're not on a water meter - it's rateable (band B) value, so this means that we could take thousands of Olympic-sized swimming pools-worth of water each day. But, guess what: we have no need for more than the tiniest micro-fraction of that, so there would be no point or benefit in our taking it anyway and stockpiling it; thus we take what we need and ignore all the rest that we don't need.
I think the saddest thing about most of the mega rich is that their money consumes their whole life and, instead of being a tool to make it nicer and easier, it becomes its purpose. A poor person worries intensely about where they can get the extra £20 they need for new school shoes or to put the heating on when it's freezing (I've certainly been there); but ironically, so many multi-millionaires and billionaires will spend much of their lives protecting what they have, fretting about investments, growth, capital share, maintaining their position in next year's ST Rich List etc. - so in one way of looking at it - their sense of inner peace - they aren't even any better off than those with barely anything.
Whatever the source of their wealth, it's largely their attitude to it that matters and, indeed, how they treat their employees and others much poorer than them (as well as paying their FAIR dues - not just what their accountants can get away with). Mike Ashley and John Timpson are both very rich men; I'm not saying that either of them is perfect, but my opinions of them both could barely be wider apart.