One of the things the Left are going to have to work through is the fact that their advocacy for open borders, mass immigration and multiculturalism runs counter to the interests of workers and the environment, which are the main things they advertise themselves as being for.
Mass immigration depresses wages and costs the native population their jobs - hard to understand why a “Labour” party would support it.
And one of the biggest drivers of environmental degradation is the size of the population - particularly if they are low income. Supporting lower levels of immigration and particularly ending third-world immigration is more in line with environmentalist goals than current open-borders thinking.
Besides, environmentalism and the trendy progressive social causes that the “Greens” focus on are things that mostly only rich white people care about - replacing those rich white peoples seems to be a bad long-term political strategy.
It seems to me that there’s no reason Western nations shouldn’t have a “patriotic Left” in place of the “Replacist” one we have now to complement the Civilisational Conservatism taking hold on the Right.