As 'books' these days, he tries to blame nearly everything related to depression and one's search for meaning for today's way of leaving.
He tells us to know we are going to die soon, get rid of the aspirations as we won't achieve the majority of them and do less for ourselves exclusively as there won't be anyone to judge that we failed.
In his opinion, this enlightenment, such a great resignation and such a terrible settlement for less is going to make us happy.

He is trying to cover everything without going to deep.
He basically touches every bit of our modern day lives without looking under the hood hence the book seem to be very shallow and lacks the 'juice'.

Last thing, Oliver.
There is this one thing you failed to mentioned in the book, something I almost consider a crime.
Consciously you failed to mention the regret at the end of it all, when people living small, who actually didn't live at all, realize they have wasted their whole lives focusing on 2-3 things and how much stuff they didn't care about.
This settling for less, return to the Middle Ages (even if only in one's imagination) costs us everything in the end.
In order to land in the comfort zone and 'forgive yourself' for being lazy, stupid and not managing it all, you are damned to end your life with regrets I wish I could avoid having.
I realize he is too young to understand it well to write about it but well, just don't buy the brochure, ok?

It won't do any good.
Strive, hunt, try new things, experience, taste, touch.
Don't settle for less.

Oliver, you will make others suffer a lot.