の無さ

lack of

→ の
phrase Rare #40,284
lack of Follows a noun to describe the lack or absence of that quality or thing.
JA: 彼女の責任感の無さに驚いた。
EN: I was surprised by her lack of responsibility.

彼の仕事を判断するには経験の無さを考慮すべきだ。

We should take his lack of experience into account when evaluating his work.

クララの責任感の無さには頭に来る。

Clara's lack of responsibility really gets on my nerves.

彼は彼らのやる気の無さに激怒した。

He was furious at their lack of motivation.