Why is our attribution wrong?
Usually because the measurement leaks before the model can say anything: UTMs filled in differently per campaign, consent asked only after the first click, and traffic arriving as direct when it is not. A different attribution model does not repair that; it moves the error.
Can we measure this without a cookie banner?
Partly, and that part is larger than most agencies will tell you. Cookieless analytics gives you visits, source and behaviour at page level without consent. What it does not give you is the individual customer journey. We say plainly what you give up.
What if we know something is wrong but not what?
Start with the New Data Scan: one day on site, fixed price, and afterwards you know where the leak is and what has to be fixed first. No obligation to continue.