Any donations you send to Mozilla today go to the corporation and are not spent on the browser. They are spent on things that have nothing to do with the core mission of the maintaining the browser.
Nobody is allowed to fund Mozilla to maintain the browser, which is the actual question you're asking.
I figure it's either worth $0, or hundreds of $. I mean, sooo much whining about privacy and telemetry and ad-blocking but ultimately it's worth the same as a couple cups of coffee?
That seems to me to be a root question here. How much is privacy actually worth? The average number in this post seems about $20. So in real terms, nothing at all.
And yes, all of this is moot given that you can't donate to Firefox in the first place.
Still, for those starting a business, this is a excellent lesson- don't confuse volume with willingness to pay. Just because lots of people shout loudly about the size of their pain, don't just assume they'll pay real money to make it go away.