Migration is a policy issue, not some natural force like osmosis.
There's a whole discipline called social physics successfully leveraging models from physics, chemistry, and mathematics to analyze and predict social phenomena. Just as the behavior of flocking birds can be reliably modeled with a few differential equations, so can a great many social changes.
https://www.sciencedirect.com/science/article/abs/pii/S03701...
It's not a "colonial nation" that is being harmed by migration, it's working class people. Meanwhile the same classes that benefited from colonialism now benifit from the wholesale destruction of communities.
Every empirical study I have seen shows that high migration lowers happiness and trust. Does that align with your pseudoscience?
working class people
I've got a feeling you're not a socialist, though.
pseudoscience
FUD
It's simply that the wealthy benifit from increasing labour supply; this is the "enrichment" you get. Not an improvement in culture or conditions, an increase in wealth concentration.
It's entirely reasonable for a citizen in an English speaking nation to complain about other languages becoming common, as it is direct evidence of the migration policy that is doing them harm.