I'm going to go against the grain and say YANBU
Buying new stuff just for the sake of buying new things because it's "mean" to rewrap things your daughter got previously is a stupid principle IMHO. Let's say, for example, that for her birthday, the OP's DD got 30 new toys, 15 of which she has never played with as they were the birthday presents that were put away. DD could then get another 10 presents for Christmas from relatives (grandparents/aunts and uncles etc) which means she has 25 more toys before her parents buy anything ... why buy more presents when you could re-purpose those 15 stored toys so that DD gets 15 presents "from Santa" for Christmas, but the overall toy count has remained the same?
It would be one thing if they had been toys that had been sitting around in the playroom/her bedroom and she just hadn't got round to playing with them because of all the other toys from her birthday, but if you put some of the toys away straight after her birthday and she hasn't seen them since, odds on she might remember one or two of them from her birthday but not all of them.
I used to have a huge issue with clutter and the sheer amount of toys DD (now 9) used to get from family for birthdays/Christmas. Our issue mainly stemmed from the fact we lived abroad and only got to come home for a couple of weeks in summer (when DD's birthday is) and Christmas so birthdays and Christmases were the main times family bought her things and spoiled her. With other children in the family, they would see them more regularly and so would give little treats all throughout the year, whereas they only saw DD a couple of times in the year so would effectively "save up" the treats and then give them all at once. Also I think some people felt that they had to compensate for the lack of personal time with DD by way of giving gifts as tokens of love instead of time.
It was overwhelming for me as an adult, never mind toddler DD so I used to do a similar thing to you OP - when we went back home after a visit to our families, we'd pack some things in our cases for DD to play with immediately and have as soon as we got home, and everything else we would parcel up and ship back to our house. The parcels could sometimes take a few weeks to arrive so when it did, instead of giving everything to DD straight away I would ration it out and introduce a couple of toys here and there; if anything wore out/broke then I'd replace it from something in storage and if there were still lots of things in storage at her next birthday/Christmas then we'd wrap a few back up and let her open them again.