So did the introduction of steam, IC, and electric machinery. Your quibble is with the OP.
Emancipation happened right around the time of the introduction of large-scale steam power.
This was not a coincidence.
Now, some might try to argue that the process of eliminating slavery/serfdom just happened to coincide with the development of non-human-powered machinery (like maybe humans just somehow became more moral and less-prone to exploiting their fellow-humans).
But you know what? That's basically just a load of crap.
It doesn't explain the near-perfect correlation between the development of powered equipment and the disappearance of slavery/serfdom, world-wide, carried out over the course of centuries, appearing first (again, apparently just by coincidence) in the more technologically-advanced countries (such as Western Europe), and later in the less-technologically-advanced countries (such as Russia, Asia, and (at that time) the United States)
Water, steam, internal combustion, and electricity is what ended slavery/serfdom. Get rid of those and slavery/serfdom will be back before you know it.
You are kind of inventing something that wasn't written. The OP wrote, "What if many of our machines used human power like they did 100 years ago, but were made far more efficient and effective than they were 100 years ago?"
We'd still have slaves. That's where we'd be.
The development of steam, IC, and electric machinery is what actually put an end to slavery, by making it uneconomic.
Slavery (or near-equivalents, such as serfdom) was a constant of virtually all human societies above the hunter-gatherer band level, until the development of powered equipment.