Then don't take a salary. Nobody is forcing you to work for a nice salary. If you want to be paid by the hour so that every hour is accounted for then go for it.
Of course, in practice that is not a possibility for most people. You can't just choose to work hourly if nobody is willing to hire you on these terms. Without regulation the balance of power is strongly in the hands of capital and inevitably leads to employers working employees to death. We have plenty of examples of this in our past.
You can go work at McDonalds right now for $20/hr where I live. You can structure your work as a consultant and bill hourly. No you can't walk into a company that is looking for a salaried employee and tell them you're going to work hourly (I mean you can try, it might work). But you have plenty of options and there's plenty of work out there.
I don’t think they were complaining about being paid per hour or not, just the expectation in many salaried jobs you work arbitrarily long hours in a competition with the nerd next to you for how much you can sacrifice for your employer.
I later in my career learned you can actually invert it by just being really effective in a shorter number of hours and work 6 hours a day and just leave the nerd next to you to expire from burnout. But it helps being later in my career and knowing how to be more effective in a shorter time.