Their old hard-won skills were irrelevant...是什么意思？

Their old hard-won skills were irrelevant...

他们以往辛苦学得的技能没什么大用处。

their

pron. 他（她，它）们的，在提及性别不详的人时，用以代替 him 或 her；

例句
Their permissiveness toward their children reflects the wild abandon of their own lives.
他们对孩子的放任折射出他们自身生活的放浪形骸。

old

adj. 老的，古老的，以前的，（用于指称被替代的东西）原来的；n. 古时；

例句
She was old enough to absent herself from the lunch table if she chose...
她长大了，可以自己做主不来吃午餐了。

skills

n. 技能( skill的名词复数 )，熟练，巧妙，擅长；

例句
He demonstrated the all-round skills of a quarterback.
他展示了一个枢纽前卫非常全面的技术。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

irrelevant

adj. 不相干的，不恰当，缺乏时代性的，落后于潮流的，牛头不对马嘴；

例句
He acknowledged that Mr Taylor's colour and ethnic origins were utterly irrelevant in the circumstances.
他承认在这种情况下泰勒先生的肤色和种族出身完全无关紧要。