Is this a typical Chinese way of saying 'lack of strength'?
Both expressions (the one you quoted and the one you wrote) are perfectly fine in Chinese.

薄弱 vs 'lack of' is a typical difference between language/culture mindsets. You can replace 薄弱 with 缺乏/缺失, which also sounds natural, but implies 'completely missing' to Chinese listeners. 薄弱 is the Chinese way to say 'somewhat/partially lack of'.