Is it? Funny, there was a time when the "left" stood for national liberation, self-determination for each people (understood as the natives of the territory). And called for the "settlers", many of whom born in those territories, to be forcibly and violently removed from said territories upon independence.
Now the "left", we are told, is supposed to stand for the end of national independence and indeed "forced colonization": an obligation to take in foreigners without any limits. This is crap and people recognize it as such. That is why you get brexit. That is why Labour in the UK is failing: because they cannot sort out their internal divisions and eject the "citizens of nowhere" from the party. May is cleaning up the Tories. Labour needs a clean-up also.
Even today the contradiction within discourses is glaring. The SNP demands independence for Scotland, under the principle of... what? National self-determination? That means the people of Scotland should have sovereignty over the territory of Scotland - which excludes pacts such as the EU, and requires a clear definition of who is part of the "people of Scotland". Or perhaps it is just a "we're better of economically as [independent, part of the EU] (which is it?). Even so, who is "we"? The SNP won't tell you. So they're sinking in their own contradictions.
Labour's leadership (nor all its MP...) calls for new economic polices. But everyone knows those polices would not be "allowed" under EU rules that limit state aid (or would be allowed only as they are for Germany and France: they're "special"...). But because it is too divisive to say "either the EU changes or we support leaving" they're unable to campaign, they can't put forth a credible and coherent programme! This is folly.