Many other countries have also not experienced such mass migrations as the UK (colonialism much?) and thus their cuisine has not changed that drastically from like 100 years ago

Dude that is what I was saying! We are agreeing!

I have had this discussion with my polish colleagues frequently given the difference in immigration levels between UK and Poland.

We always note the irony of Polish people being one of the largest migrant groups in the UK now, but the food and traditions being poorly integrated. (That said you can get some wonderful sausage and cured meats at supermarkets now that we can thank them for).