I don't necessarily think parents should explain anything to people who are kind enough to give children a gift (unless the person asks before selecting a gift).
When children get a new toy they either enjoy it for a short time and then lose interest in it, or else they absolutely love it. If they love the toy it's up to parents to keep an eye on how much time they spend on it (and whether that's a good use of play time or not); and do a little "managing" when it comes to limiting how much time a child can spend on certain kinds of toys.
I think most kids young enough to be playing with toys lose interest in most battery toys anyway. If they don't lose interest before the batteries run out, there's always saying, "Oops. The batteries are dead. We'll have to get some more of these days. In the meantime, maybe you'll have to do the talking for your doll." (That kind of thing.)
Personally, I don't think whether toys irritate adults should really be an issue, but if it must be there's always letting the child play with the toy while it's new and arranging for it to be "misplaced" (maybe in back of the tall bookcases) once the child isn't looking for it regularly.
If a toy is believed to be too stimulating, the child is young enough to be over-stimulated (and therefore, young enough for parents to set the toy aside somewhere); or else he's an older child who is old enough to understand some time limits placed on that particular toy.
Some parents complain of storage problems, but there's usually a way to organize toys (or set some aside somewhere) in a fairly workable way.
So, to me, I don't see the need to risk sounding ungrateful or risk coming across as someone who just feels the need to make sure someone else knows how little he thinks of the other's idea of a gift. I don't know... there's something to be said for a parent's knowing how to be gracious and flexible, set some limits, explain some things to children, and generally enjoy having others around who want to make one's children happy by giving them a gift. With three grown kids, I've seen more than my share of gifts from grandparents and others that I wasn't too thrilled with. It was only rarely that a gift I didn't particularly think much of required action on my part. Most of the time, nature (as they say) takes its course and the child moves on to something different soon enough.