Is wealth inequality necessarily bad? Genuine question here.
As with everything else in the universe, it works for some, it doesn't work for others and there are plenty who have almost literally no opportunities for whatever reason.
In western nations we think that most people have basically the same opportunities but if you are from a low-income family, you are likely to have more issues with your family, potentially more emotional and financial dependents. If you have been knocked back too many times, you can lose confidence and not have anyone to encourage you.
I guess in moderation, wage differences can motivate but at the point someone drops too low, they easily get caught in a cycle and then it becomes societies problem.