Mass immigration is just another government program, and everything the state touches it turns it into a cancer in no time. (money, education, health etc)
What is happening today is not healthy anymore, it is about depleting poor countries of their most valuable resources, their young productive people, thus making those already poor countries even more dependent. It is another excuse for printing more money (8M£ daily in the UK!). It is a heavy and unsustainable burdens on the infrastructures of the welcoming country.
Yes to immigration, no to government controlled mass immigration.