Genuinely interested: are you a developer? Doesn't sound like low-hanging fruit to me.
There are already many alternatives to Gmail, I don't think Mozilla would make a lot of money there. And I don't know if they are making a lot of money with their Mozilla VPN (which I understand is a wrapper around Mullvad): why would I pay Mozilla instead of Mullvad?
There are alternative search engines, like Kagi in the US and Qwant/Ecosia in Europe (though only Qwant seems to keep the servers in Europe).
What I want from Mozilla, really, is a browser. And I would love to donate to that specifically, but I don't think I can.