Immigration is driven by people and circumstance. We have been importing labour and skills since - well, the early 1800’s with the Irish - and exploitation of that labour is often part of that equation, but there is nothing to stop the accepting country ensuring that conditions and pay are acceptable and exploitation is minimal.
A population that is hostile to immigrants - no matter how necessary - will be a barrier to fair treatment. ‘Immigrants get it easy/are favoured over native populations etc’ allowing Govts and business to exploit/mistreat immigrants. The UK is a classic of this genre. We spend half our waking moments bemoaning immigrants/freedom of movement, made ourselves miserable in the process and ended up with record levels of migration (okay, still makes me laugh). It also has landed itself with a Govt legislating that the earth is flat, Rwanda is a paradise and is no longer processing asylum applications because it can no longer perform the basic functions of Govt. Another feature of battling reality is that it erodes basic competence.
In short, I’m just pointing out the reality of how the world works and what a developed country like the UK needs to function. You are free not to like it - I’m not keen on how some things have turned out either - but reality, alas, doesn‘t care.