It is objectively true that women are overrepresented in lower paying jobs. This is due to a variety of reasons, including societal and social factors thay discourage women from going into higher paying, traditionally male fields. The gap is narrowing especially now that, at least in the US, there are more women attending university than men and we have robust laws to prevent/punish discrimination based on sex.

Here's a good summary/explanation by Pew Research Center in a writeup of a survey of theirs on the Gender Pay Gap:

"Much of the gender pay gap has been explained by measurable factors such as educational attainment, occupational segregation and work experience. The narrowing of the gap over the long term is attributable in large part to gains women have made in each of these dimensions.

Even though women have increased their presence in higher-paying jobs traditionally dominated by men, such as professional and managerial positions, women as a whole continue to be overrepresented in lower-paying occupations relative to their share of the workforce. This may contribute to gender differences in pay."

They go on to say that a gap still exists, even accounting for these factors, but it's smaller than the commonly cited 84% figure (though 84% is correct if you don'taccount for other factors).

https://www.pewresearch.org/short-reads/2023/03/01/gender-pay-gap-facts/

The US government has found that "Specifically, differences in the industries and occupations where men and women work explain 42.0% of their variance in earnings. ": https://www.dol.gov/sites/dolgov/files/WB/equalpay/WB_issuebrief-undstg-wage-gap-v1.pdf (source on the chart in page 2 of the writeup, comes from 2020 study by the US Census Bureau)

Here's a brief writeup of a Harvard study that talks about how women self-select into lower-paying jobs: https://gap.hks.harvard.edu/effect-task-choice-and-task-assignment-gender-wage-gap-experimental-study

Basically, there is a pay gap, some of it is explained by factors other than gender, but we should work to try to eliminate those factors by removing barriers for women to enter certain fields as well as gender discrimination.