While I sympathize with your disappointment at receiving a rote response from a seller to thoughtful feedback left by you as a buyer, often the sellers who choose that phrase have enabled ebay's automatic-feedback feature. This means they never forget to leave feedback for their buyers, and that's better than not receiving feedback at all. Some sellers don't bother to leave feedback. Even more buyers don't bother.
It is important to note, like Vivian said, that sellers can't say much aside from a polite "Thank you."
I try to vary it a bit. If the buyer is new to eBay, I'll say: "Welcome to eBay. Thank you for choosing McQueen and Mo Mater." If the buyer is French, I'll say, "Merci beaucoup! Thank you for choosing McQueen and Mo Mater." If German, it's "Danke schon!" et cetera. Local pick-up? "It was a pleasure to meet you!" That kind of thing.
A seller can't really say anything personal to the buyer without getting into trouble. For example: "Thanks, Billy! Sure hope that toenail fungus ointment does the trick for you!" would get the seller into hot water for two reasons. The first being a reveal of the buyer's first name, the second a potentially embarrassing detail of their purchase history. Although I sell nothing worse than toys, I'd still be reluctant to share that detail in feedback in case it was meant as a gift. Never mind leaving feedback that says: "Hope you enjoy the xxxxl ladies underwear!" or "We guarantee you'll love our blow-up dolls!"
Know what I mean?
As a matter of fact, I've seen buyers leave negative feedback for sellers based on the seller having to accurately declare the contents for Customs of the order in the box -- a legal requirement-- if the order contained sensitive items. Simply because it's crossing a border, it has to be declared what's inside no matter what it might be.
To some extent, the seller's hands are tied. I know it isn't their intent to offend with bland feedback for buyers. Quite the opposite.
