In the light of many adult children not being able to visit their aging parents frequently, many old people have to endure loneliness.

【翻译】鉴于许多成年子女不能经常看望年迈的父母，许多老人不得不忍受孤独。

1. being 很重要，不可省略。它是构成动名词的重要手段和唯一成分。没有 being 属于语法错误，of 后无法直接跟 形容词 able 作宾语。

2. In the light of ... 是个短语介词，意为“鉴于；由于”（because of），后面接名词或动名词。many adult children not being able to ... 这是带有逻辑主语（many adult children）的“动名词复合结构”，作介词 of 的宾语。

我举一个类似的例子：

I didn't sleep because of Tom snoring. 

由于汤姆打鼾，我一直未睡着。