How to phrase authors' contributions when the convention is that all team members are authors?
If there is a requirement to list the contribution of each author, it seems the ethical way to handle it is, well, to list the contribution of each author.  If some authors did not contribute directly to the paper, you should state that.

It is unethical to try to conceal that some authors did not make a direct contribution.  Please note: Your team policy is what it is, and I'm not trying to judge the ethics of your team's policy.  I'm just saying that, whatever your team's policy is,  you must disclose it forthrightly, without evasion.  That's exactly the point of disclosure requirements!

(If you're not comfortable stating your team's policy explicitly, that might be a hint that it's time to consider changing the policy -- but until then, you must disclose it frankly and honestly.)