I won't downvote you but I think people are because it's a pretty perfunctory claim, not to mention inflammatory, that 'extreme inequality' A) applies to the West or B) is plaguing the West (for whatever we mean by 'West' which itself is pretty broad strokes). But you seem to be mainly making a point about Nigeria, and to be fair, the trend in Nigeria is really bad. But also, to be fair, it's also an aberration as far as global poverty is concerned. The % of people living in extreme poverty has dropped from 44% in 1980 to < 10% today.[1]. Nigeria seems to be a rare exception where absolute poverty is increasing rather than decreasing.

But there seems to be an assumption baked into your point that inequality is the problem to optimize for, rather than actual poverty alleviation. And of course wealth inequality doesn't correlate very well with absolute outcomes in economic wellbeing. Cambodia has very low income equality (Gini index of 30.8%) and very high percentage of people living in extreme poverty (6.15%). Brazil, on the other hand has very high Gini index (51.3%) and very low percentage of people living in extreme poverty (0.5%). Those numbers are just from Wikipedia but there are plenty of studies done on how useless 'inequality' is as a measure of real world outcomes.

[1]https://ourworldindata.org/wp-content/uploads/2013/05/World-...