One player can't get you to CL. That's not Palacio's fault.
I was like you, disappointed when we got Palacio, but mainly because it felt like we were moving even further away from top signings and going back to the ridiculous logic of getting any Serie A player of the moment. But, I was wrong and if Eder proves to be as good as Palacio I think this would be a good deal. But it's a tall order. After Handa, Palacio was one of the few solid post-Treble signings.
Eder is bad because we need something else more, because it means giving up on players we already have on account of Macnini being clueless to get them to work together productively.