That link is for Mozilla Foundation, which is a non-profit and donations to it do not go to the development of Firefox. Mozilla Corporation, the for-profit entity, owns and manages Firefox. The way to support Firefox monetarily is by buying Mozilla VPN where available (this is Mullvad in the backend) and buying some Firefox merchandise (like stickers, t-shirts, etc.). I think an MDN Plus subscription also helps.

New this year? https://web.archive.org/web/20250000000000*/https://www.mozi...

I agree it's counter-evidence right now, and I think there has been a way to donate for a long time now (just to "mozilla", not "firefox" or setting any restrictions), but I'm not sure what the historical option has been...