It's not clear to me that you're saving much of anything by using, for example, a washable duster versus a disposable duster. It takes a lot of water to wash things at your home. It doesn't take very much water to make a box of disposable dusters. Etc, etc.

K-cups are decidedly bad, because they waste plastics which are non-renewable. Dusters could be made, today, using only renewable resources.

I googled around and it seems the swiffer cloth has never been compostable.

As in it's made of plastic? Ooof, I retract my statement.

Well water isn't trash, so just by virtue of producing the swiffer it's creating more waste than the alternative.