Everything (or everyone) can be useful if used appropriately; usefulness depends on how something is used.
アイデアは単純でも使い方次第だ。馬鹿と鋏は使いようだ。
Even a simple idea can be useful depending on how it's applied. Everything has its use.
彼は飽きっぽいが、うまく教えれば役に立つ。馬鹿と鋏は使いようだね。
He's fickle, but if you teach him well he can be helpful. Everything depends on how you use it.
古い道具でも工夫すればまだ使える。馬鹿と鋏は使いようという言葉がある。
Even old tools can still be used if you are inventive. There's a saying that everything has its use.