The article's author isn't saying the book is morally wrong for only taking about white european males, they are only saying that might be a contributing factor

The article's author isn't saying the book is morally wrong for only taking about white european males, they are only saying that might be a contributing factor to explain why this book is not often read, namely that few people can relate to the characters of the book, which is pretty important for self-help. Seems to be me you are a bit too quick at signalling virtue signalling.