At least he has the honesty to say that he doesn't have a fix and that some of the proposed fixes aren't going to work.
I think if Europe hadn't been an abusive colonial power over much of the rest of the world for centuries, then this whole immigration question wouldn't figure so prominently in recent times.
I'm not sure having multiple cultures in a country is necessarily a bad thing but it can be a mistake not to be able to recognise the issues or treat people accordingly. Like Singapore is a successful very multicultural society but if immigrants/expats do bad stuff they get kicked out rapidly.