If you agree to work for a wage and you can leave at any time, you've eliminated the two key points of slavery.
most people are dependent on their wages. this means they don't have a choice about whether to work for that wage, and they really can't leave
And? You think that before there were wagesthat everything people needed just fell out of the sky and landed at their feet? People have always had to work for things they need. Whether directly acquring them through hunting and living off the land, or indirectly by working at a job for money.
It's amazing that because people actually have to be productive in someway in order to get the money that they need you'd use the term "wage slavery" unironically. Yet you're completely comfortable with government aid where people are being forced by law to turn over part of their income to be used to pay for other people's living expenses.