Welcome to the community @Sebastian468
Klaviyo does not support 1-click unsubscribe. I believe this is due to some receiving email systems that click through all the links in the email to look for malicious code on the landing pages. I see that type of activity on B2B emails and also emails on educational domains. In those instances, a 1-click unsubscribe would opt-out contacts without them intending to do so.
Nor can you send a confirmation email once a contact has unsubscribed because they’ve opted out! That approach would risk upsetting contacts and could result in spam flags.
However, the current unsubscribe mechanism pre-populates the unsubscribe form with the recipient’s email, so a good compromise, I think.
I don’t think it is likely that someone would unsubscribe using another person’s email either: the static part of the unsubscribe url gives a 404, so they’d need first to have a Klaviyo-generated unsubscribe link; someone else also in a Klaviyo list. That scenario is very low risk, in my opinion!
Hope that helps
Andy