What about telling someone they’re being rude for telling someone they’re being rude?
I dunno, I find it kind of much to be giving Auntie Jane the benefit of the doubt in a case like this. I mean, maybe she’s a cool aunt who’s going to teach you some lesson about life by giving you socks a la learning karate without practicing like Daniel-san. But isn’t it more likely that Aunt Jane remembered your birthday in a haze of booze and cigarettes the night before, and the only thing open at the time was K-Mart, and in her drunken stupor she thought that kids really really like to make sock puppets, and besides, they were on sale?
I understand that it’s annoying to feel like your gift is being judged, and of course it’s the thought that counts. You should be nothing but respectful and grateful for any gift you receive. But if the giver never finds out, I don’t see how it’s disrespectful.
That’s certainly possible. But in my mind, that’s the deference a gift-giver gets. Sure they might have been blindfolded, stumbled through the dollar mart, picked up the first package they touched, paid and stuck it in a box - but you should always have the grace to believe that they took their time and thoughtfully selected the gift with you in mind.
There are exceptions, sure. Spouses should know that their SOs don’t fish or go bowling (a la Homer Simpson) so those type of gifts are tacky, and they should be humiliated for trying to perpetrate such fraud.
So how long do I have to hold onto all the crap people (quite generously and lovingly) give me before I appear on a midday talk show about hoarders? 
I’m working very hard to reduce the amount of stuff I have, not increase the ratio of useless crap.
Actually, what I most often do is enthusiastically thank the gift giver, and then I do take back much of what I’m given, because it’s most often the wrong size (people always underestimate my clothing size - ouch!) or style or whatever…and then with those gift cards I buy presents for my kids. I don’t have a lot of present-buying income, so this makes their holidays more enjoyable, which makes me far more happy than a size medium sweater with kittens on it would. I’m lucky - they have January and February birthdays, so between my birthday in late November, Christmas gifts and after-Christmas sales, my kids have no idea we’re really as poor as we are. I spend my money at Christmas and returned-gift gift card money for their birthdays.
My family are far too polite to ask if I liked it after the fact, but I have had a couple of friends bring it up. When that happens, I’m polite enough to tell them again how much I enjoyed receiving it (which is true) and how thoughtful and sweet they are (which is also true) and not mention whether or not I liked the item itself. They’re distracted by the flattery and don’t seem to realize I never answered the question. It’s worked for me for 15 years now.
If the person is visibly ungrateful, opens the gift and immediately begins rummaging around for a gift receipt - that’s tacky.
But if publically, the person graciously accepts gifts, lights up upon opening the package, thanks the giver for the thought and action of choosing a gift, and acts as though they are lucky at having friends who will give them things… why should they be stuck with something they really don’t want?
The only thing that comes across as tacky is that you seem to know that she exchanges gifts. Is she bragging about her gift exchange abilities? That’s tasteless. But if the original gifts just aren’t staying her possession for a very long time before discretely finding their way back to the store, no big deal.
No, it’s more likely Aunt Jane is a bit strapped for cash, and she knows you need socks. She might have given underwear and t-shirts, but kids grow so fast, and she knew the socks would fit.