>I left not long after and so did many others.The question from me is, did you manage to move to a company where you got paid the same or more, but for "a day less hours"?
Employers can make that claim if the job market is in their favor, i.e. if most other companies agree with them and decide that they need staff available Mo-Fr 9-5 or for less hours but also for proportionally less salary, which to my experience is most employers.
To normalize this, we need the majority of employers (>51% of them) to switch to paying market rate for less hours, putting pressure on the rest that this is the new norm, but I haven't seen that yet in my EU country, except for a notable couple of companies that made headlines, out of which one recently filed for bankruptcy. So as long as only a tiny minority of companies are doing this, the norm will not change. All businesses here think like your ex-boss: 'Why should I pay you the same for a day less?’ and the market favors their approach as they have seen no mass resignations since they all can afford to act like this.
Therefore, the only solution would be the same as the one that lead to the 8 hour workweek being normalized almost 100 years ago: mass strikes and labor movements followed by government regulations that makes the 4 day workweek the new norm for everyone.