There's definitely a difference between "Cookies provide X value" and "We were able to mitigate the loss of cookies by doing A, B, and C - but we don't know the value of doing A/B/C individually."

If the point is to quantify the value of cookies then you need to measure that as an independent variable. Attempting to compensate with other actions, each of which you also don't know the independent value of, means you will be unable to quantify the true value of cookies or the value of your other actions.

What if none of the tools they're using, including cookies, provide any measurable value? How would you know? What if the value of cookies (X) and item A is positive in terms of impact, but B and C are both negative, but not enough to offset A so it comes out in a wash?

This seems to be very much the case for behavioral ads as far as I can tell. At some point Google et al convinced everyone that tracking the user's every move across the Internet made for better conversions than just providing ads that are relevant to the content they appear alongside and everyone just nodded along. Given that we now know that Meta (née Facebook) blatantly lied about the effectiveness of video content (which single-handedly killed various news sites who made hard pivots based on these claims) I'm not convinced behavioral ads really do perform that much better. The biggest value add of Google ads was that it provided some safeguards against abuse and a reasonable expectation of safety and moderation.