I think this is an overly cynical take on a promise that either was never made or made cynically without an expectation that sophisticated employees would take it seriously.

If you draw the 2x2 of Good for Employers & Good for Employees, ERGs can be helpful in pushing incremental changes that are both Good for Employers & Employees and reducing stuff that is Bad of Employers and Employees. It probably can't nor ever really promised to work on issues that are Good for Employees & Bad for Employers and that's rightfully where unions play a role and of course executives are already hired to work on the segment of Good for Employers but Bad for Employees.

As long as you approach ERGs with this understanding and also the additional understanding that, at most companies, when dealing with marginalized groups, there are plenty of Good/Good and Bad/Bad issues that deserve work on. ERG groups are pretty forceful in pushing employees away from Good/Bad issues, even if they are more important issues to work on because the purpose of ERGs is a channeling force to focus on the Good/Good problems.