when you’re given a gift it’s not about you, it’s about the thought and effort someone else has put into getting something for you.
Really?! I'm gutted. I thought gifts were about the recipient!
A couple of DH's relatives always give me a bottle of champagne for Christmas. I have been basically teetotal for a decade. But I know that we don't know each other well, so it isn't at all hurtful that they miss the mark, and it's useful to have a spare bottle of fizz lying around for when I go to someone else's: in effect the present they have given me is the time and money I'd have spent getting something for my friend, and that's something to be grateful for.
But when someone who ought to know you gets you something way off the mark (clothes you'd never ever wear, or something you're allergic to, or an ornament you hate) then it rocks your understanding of your relationship with them. In some cases as pps have pointed out it's because they are trying to change you, or because they're gifting to their image of you which you can never live up to. That hurts because you see it as a direct criticism of yourself or how you live your life.
PIL tend to give me vouchers now, as I've been carefully exuberantly grateful for them in the past. Exchanging money is slightly pointless, of course, but I'm far more able to justify spending a voucher on myself than cash so it does end up being a treat (as opposed to their spending the same amount on actual goods in the same shop which I then exchange for less than they spent because they have since gone in the sale).
I don't think I'm particularly good at giving presents, except that I know I've had a few notable hits and I avoid giving anything which puts an obligation on the recipient, so no ornaments which would need to be displayed, for example, and consumable things like chocolates/wine/hand cream so they can easily pass on or swap or use up and not have hanging around forever. Children over around the age of 8 just get cash or equivalent because bloody hell it's what they want and they have very few opportunities to get any otherwise.
OP is clearly at the end of her tether for reasons not to do with MIL. Of course her reaction was unfortunate, but she did her best afterwards, and sometimes it's healthy to show our true emotions.