Sad, neither country wants millions of people they probably can't feed or employ. I'd wonder if it would be a better use of "human resources" to let undocumented folks work for their citizenship... a win-win. They'd have labor for projects (infrastructure, farming) and documented/taxable revenue sources.
On one hand if I were to sneak into Italy and one day be caught, I would expect to be deported. On the other hand, if you married (and had kids) in the new country and lived there for 30 years, it's really hard to accept that.