Totally agree! It's not a huge demographic, but offering this as a cheaper alternative to the Audi/Volvo/BMW/Merc wagons should have been the natural marketing angle. As you mentioned, pets is a big one, particularly considering the lower cargo height. I'd also picture a farmer's market visit.
But the reality is that Volvo barely advertises their wagons, and BMW/Mercedes/Audi pretty much don't either. They all have an established lineage where anyone who might want one already knows they exist.
I don't know that the model name would have changed things much, to be honest - I think it's merely a lack of advertising and the Buick brand name in general that's holding it back as much as the inherent wagon-ness. I think this is a 'rose by any other name would still be completely unnoticed without advertising' if you'll pardon the paraphrase.
It's a running joke that I'm under 40 and I bought a Buick... so much so that when it comes up in discussion that I recently got a new car, I lead off with "I bought a Buick!" just because I love seeing the puzzled faces of people. Almost nobody knows what a TourX is even when I tell them.