Some groups are a big net benefit to our (looking at the income the group benefits / social support costs) and others slight net negative. But once you take the economy into account it's positive.
So no, most migrant groups are not a big benefit. Especially considering that this is only taking the economy into account. When you take into account the societal disruption and anti-values that they bring with them, then its clear how negative they have been for Europe.
The Dutch were happy to do those jobs 50 years ago.
After every single "jobs the natives won't do", there's an unspoken "for the dogshit pay we offer."
It all sounds great until the last 40+ years goes away, with the apples year round and bananas, etc.
Going back to just what you can produce in your country is gunna be a rude awakening for billions.
You could force people to accept the low wages by removing all welfare but that has its own problems.
These are all hyper exploitative industries based on capital exploiting the poor. Which is something we both agree on.