So many things wrong with this.

The work week is, at a basic level, tied to productivity. The rise of the salaried class represents an end-run around overtime requirements in professions that aren't protected by unions. In order to protect people for working less than they are now, trade unions would need to become dominant and uncontested. Those who see this happening easily are advised to study the Pinkerton riots and assorted strikes and melees associated with the International Worker's World.

Suppose they did, however. The basic argument put forth is hidden deep in the text:

nstead of endlessly growing GDP, maybe we need to recalibrate society to make more people happier and successful with less.

In other words, "get used to the wages you can earn working part-time."

There's a great HL Mencken quote: "a wealthy man is one who earns $100 a year more than his wife's sister's husband." In other words, we don't judge our wealth based on what we have, we judge it based on what our rivals have. Unless you actively prevent people from working - at all - in their spare time, "hobbies" are rapidly going to become the new industry and your labor market ceases to be regulated.

There's nothing wrong with working 40 hours a week. There's nothing wrong with working 50. The problem is working 40 or 50 hours a week doing something that isn't fulfilling that doesn't compensate you adequately and provides no safety net. The problem is not that people are working too much, the problem is that work sucks.

Restricting hours will not solve this.