A good statement from the American Association for the Advancement of Science (publisher of Science):

Gold OA journals, for which authors pay publication charges, work for senior scientists who are well-funded, tenured, and overwhelmingly male and white, but not so much for early-career scientists who may be poorly funded, not yet tenured, and much more diverse. Also disadvantaged are scientists at smaller schools, including historically Black colleges and universities, and in underfunded disciplines like math and the social sciences.

But the AAAS statement implies that its (mostly) subscription model is the equitable alternative. But that’s willful ignorance: direct, collective funding removes the barriers for readers and authors.