The big question is:
Does the money go to Firefox or to funny projects and (what I consider) insane exec salaries?
Yes, Mozilla (.org) is a non-profit, and Mozilla (.com) is a regular corporation. Yes, Mozilla has commitments about transparency. Yes, exec salaries are insane.
Do folks who ask this question scrutinize every purchase or business they make to this degree? In the laundry list of entertainment, learning, and professional subscriptions, what portion of spotify, github, or other popular subs end up contributing to just the feature or service you like as opposed to the entire organization and other initiatives that the organization supports?
If they did, the donations to some charity type orgs would probably drop to 0. Lots of unhappy people about the pink "awareness" org and others that spend as much money doing the events and paying for staff than doing anything else. Yes, we're "aware" of breast cancer.