A good QA actually does the work that product managers should but don't, in terms of understanding actual users and checking the feature delivered matches actual user ask.

But I've worked at places with a whole spectrum of coverage in roles spanning Product Mgrs, Project Mgrs, BAs, QAs, production support level 1, production support level 2, etc. The one constant is whatever is missing or understaffed just ends up getting done by engineers.

Testing, on-call, Jira managing, requirements gathering with users, analysis, etc... all falls on to engineering. Then management gets even more wound up about dev productivity/velocity, etc.