Blaming the EU is a common escape strategy, but I don't believe it in the slightest. Mind, I wouldn't believe anything coming out of the modern Google except "we want to make tracking you easier so we can sell more expensive ads".
Edit: if the evil EU "forced" them to require a credit card or my ID to watch Samuel L Jackson saying "motherfucker", why hasn't the same evil EU forced them to make it easy to opt out of all tracking?
I suppose if you have verified your age in the past (for example if you bought something from the play store?) then you can watch the video freely. Try and watch it while logged off.
https://support.google.com/youtube/answer/10070779?hl=en-GB#...
Credit cards in the EU are not very prominent as a payment method, mostly for paying USA companies.
You don't need anything. At all. According to Google, in case they suspect you might be lying about your age, they _might_ require age verification. This can be done with a credit card or an ID card.
So no, you don't need a credit card to watch age-restricted videos. You don't need a debit card either. You probably don't even need an ID card or anything at all.