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?
Yes. When you are paying for something, you should have an idea of where that money is actually going. That is why it comes up here. There isn't anything exceptional about this case with Mozilla.