You can prioritise other things, but that fact is a fact - immigration grows the economy.
Overall this is true, not least because many immigrants work in highly paid specialties such as medicine. However simply to say it is an economic benefit without qualification is to ignore the fact that there are some areas where significant immigration leads to greater deprivation and overcrowding. Areas where immigrants are poorly educated, speak little or no English, can only get very low paid work at best, no work at worst, and where they form aggressive and hostile ghettos. See (The Casey Review) and the unrest in the Sheffield Hallam region between different ethnic groups.
Now this may, as Casey suggests, be a failure of successive governments to implement a thought out plan to manage immigration and social cohesion, but it is also true, as again Casey notes, that many immigrants bring with them strongly held views on the role of women, on tolerance for others, and whose values differ from those of communities already living there. It is also not disputed that in areas where immigrants are found in large numbers there is a perceived unfairness in the allocation of scarce housing resources.
So I think we have to be careful about being too dogmatic that immigration is of national benefit without considering a more nuanced, local, view.
The proposition that we need immigration to care and provide for the elderly also bears scrutiny. Those younger immigrants providing those services will one day be elderly themselves and also needing care. Where will that come from if not through further immigration and yet more pressure on resources? Can population expansion be unlimited, or will there come a point where need for resources outstrips supply and simply cannot be met?