Even if you wanted to financially support Firefox or Thunderbird development through donations, there would be no way to. Your money will go to the Moz foundation, and end up in all sorts of endeavors except the ones you care about: Moz spends money on discontinued mobile operating systems and new languages and language runtimes (Rust, WASM) nobody needs (sorry Rustees). Above all, your money likely goes to salaries and pension plans for CEOs and upper management.
When it has been suggested many times that Moz just needed to put the money they got from Google into a fund to finance FF development.
As to TFA's point about "sitting on the table to decide about web standards", that also hasn't worked out. It hasn't helped to keep "web standards" in check, nor did Mozilla's own contributions become part of them. All in all, Moz just acts as a fig leaf for the web end-game, pretending there's a community or some such.
With respect to "web standards", our best bet could be to demand that W3C, WHATWG clear up their shit and publish formal standards (possibly in an executable language to base a new formal browser/viewer app on). The way it is now helps no-one except Google.