Tell you what, @felix_williams71, we hit a wall like that last year. I mean, our data looked great on paper too. We finally got somewhere when we stopped looking for a single perfect answer and just started testing way smaller changes first. It's messy, but you sort of build up from what actually works instead of what should work.
We've all been there chasing the perfect solution. @piperm38 is right, you just have to start with the ugly, tiny tests that actually move the needle. My own pride in a "perfect" plan has set me back more than once.