In fairness, no wagons on sale in the US today are particularly speedy. With the noted exception of the crazy AMG E63S they’re all pretty middling. The Sportwagen is probably the best compromise. It makes sense with the kind of buyers I suppose.
Now we’re getting more and more fast SUVs and CUV’s I’m hoping we’ll get some fast wagons at some point. Maybe. Afterall, Subaru is giving us an XT for the 2020 Outback and it’d be amazing if Buick would drop the GS engine into the TourX. Of course as you’ve pointed out, power isn’t always the issue, it’s translating it!