I'm curious what job you have. I'm a SWE who is in the process of moving into a manager role. As an IC, I am 100% certain that I could get the same amount of work done in a 24 hour work week. In fact, I was probably working less than that already and still meeting my deadlines and getting great reviews. As a manager for the same team, at the same company, I am now working a full 40 and there's no way I could cut 40% of my hours without a massive drop in output.
I'm not against a 4 day work week (in fact, my manager is talking about trying it out in Q4 for our department), but not everyone is an IC knowledge worker. There are plenty of roles where time does directly correlate with productivity, which is why this discussion is so complicated.