It is not about the Kafala system, since even the West has similar systems. It is that they treat migrant workers that are not highly skilled specially from specific backgrounds bad.
In Saudi Arabia, Gulf States, and elsewhere in the region migrant workers have their passport taken by the employer and thus can’t leave the country. They are stuck. In most other countries the employer does not confiscate your passport. It’s weird to me that one needs a passport to leave a country. In the U.S. you don’t need a passport to leave.
If you’ve ever been to a GCC country, you’ll notice that passport control when leaving is extremely long. It’s filled with South Asian men (and some women) who are put through the ringer by the officials and often pulled aside for extra questioning before being able to board a flight. They all seem to be on pins and needles
That's not legal, and it doesn't happen in cases of the kind of workers you are talking about. Taking passport or treating to be accused of rape and similar things happen (not commonly) to domestic workers and drivers. In occasions they buy the right of Kafala from the Kafil for a couple of $1000s and you leaving before your contract ends feel to them like a loss of money, I would say the situation here is indeed similar to slavery. For industry workers, every worker is replaceable and the company hiring you has 0 incentive to force you to stay.
The real issue in gulf is not paying livable wages mainly. Anything else is comparable to farm workers in Europe.
They can (and often do, at least for deportations from the UK) demand to see evidence that the deportee is, in fact, one of their citizens. Which can be difficult to prove without a passport. We have people who have been in immigration detention for years because they won't cooperate in getting an emergency travel document, or their 'home' country doesn't accept that they have a right of admission there.
No, the West does not have similar systems. There is plenty of injustice in the Western treatment of immigrant workers, but it's nowhere close to the outright slavery taking place in the Saudi peninsula. To point out injustice in the West is fair, but to use that to excuse the level of injustice in Qatar is delusional.
It's not just migrant workers thought, my one cousin who is a white collar worker, making significantly more than me, lived under similar conditions with respect to passport and living...they even go through his mail. I have had other cousins in the are who have worked as labourers and the first hand accounts as bad as we've heard.