You’re not supporting development, you’re supporting a rich guy getting richer:
Interesting to note that the Mozilla CEO earned nearly as much ($5.6 M) as Mozilla received in donations ($7 M).
https://lunduke.locals.com/post/4387539/firefox-money-investigating-the-bizarre-finances-of-mozilla
Depends where you go. My Czech bank card is a debit card with a number on it that you can use like a credit card. Dutch banks don’t have this and we use different online payment methods. I never really needed a credit card for anything (until I traveled in France) so the price to have one is not worth it.