Underlying the claim is an assumed egalitarianism. How much is "too much" and how few is "too few?" Obviously those making the criticism have some concept in their minds of how they would like to see wealth distributed in society, and it seems they would prefer a more equal distribution than is currently the case. The obvious question is "Why?" The answer often given is that this would be 'fairer', but since they seem to define 'fairer' as 'more equal', this is not very helpful.
It does not help, either, that many of these measures of inequality only count certain forms of wealth. Many people in the UK see equity in housing as their main source of wealth. For some it is pensions. Many assessments of wealth distribution, on the other hand, only count assets and investments, and thus miss much of the wealth owned by ordinary people. Few if any seem to count entitlements to such things as health and education as part of measured wealth, even though they undoubtedly improve the living standards of the average citizen.
It could be argued that societies with an unequal distribution of wealth are able to increase wealth faster, and that poorer people in those societies become richer more rapidly than those living in more equal societies. To poorer people it matters that they are able to command more resources. It matters less to them that software multi-billionaires have widened the gap between them and made society less equal.
Part of the reason this criticism persists is envy, the resentment that some have more, yet aspiration is often motivated by the observation that some have it better. The success of others can inspire the desire to emulate instead of simply envying.
The false zero sum game probably plays a role in this criticism, the notion that because some own so much, the rest must make do with less. In fact wealth in constantly being created, and creating wealth is a far surer route out of poverty than redistribution. Instead of envying those richer than themselves, people would be better advised to try to copy them.