I personally don't believe that we live in slavery, even when we are not using that word rigorously.
Man is free at all times, as long as he wishes.
The man can choose if he has a job or if he does not want to, as long as he can stick to his results. Nothing prevents you from going to a forest and living naturally, or from sowing in your home and living off self-consumption.
But if you want to have a life with the material wealth created by the free market, then you must adhere to the rules of the free market, I don't say that this is good or bad, I only say that you can not expect to live on the wealth created by a system, if you don't want to cooperate with him.
work is dozens of weekly hours dedicated to a cause that is not particularly of benefit to you
In fact, the cause you work for is particularly beneficial to you, only not directly. The fact that you work to meet the needs of others, makes others work to meet your needs.
The ancients worked only to meet their needs directly, what was the result? their own houses were built, they sowed their food, they lived on self-consumption. But they did not have telephones, they did not have cars, they did not have luxuries, because there is no man on the planet that can do any of these things by itself.
Milton Friedman puts the example of how nobody is capable of producing by itself not even a pencil.
I think that if there are many slaves today effectively, but it is only because they wish so. Always in history there have been slaves of the type "if I get rid of my master, who will give me the food? where will I live? what will I do?", so as you can see, many people like, indirectly, to be slaves.