Taking time out of life to write a book about the wonders of living in a cabin, is about as imbued with false grandeur as one can get.
Had Thoreau taken on adult responsibilities, his incites would have been far more impactful. But then he would have realized that most everyone already understood those incites, making a book unnecessary.
It is most interesting that Thoreau had his naturalist epiphanies, while most of America still earned a living working under the sun on farms all day.
He didn’t make any grandiose claims for it nor did he claim that everyone should do it. It was a personal recollection that has been philosophically and ideologically magnified after his death.