I look forward to buying her book. I first came across it when Benjamin Hardy mentioned it in his own book, Willpower Doesn’t Work.
As others have said, I think it’s possible to bridge the gap between “mottainai” and Kondo’s throwing-away. To get to a place where we can practice mottainai, we must first be rid of the things that we do not need.
There is waste of space, there is waste of time maintaining and cleaning things we do not or cannot use. I’m not familiar with Kondo, her show, or her philosophy, but maybe a good suggestion would be to first try and find people who ARE in need of such things, or finding a means of recycling them, before trashing them.