Labour rhetoric. The UK isn't "barely functional", that's a ludicrous communist fantasy that can be traced back right to Marx, who tried to convince his readers of the dire near apocalyptic state of England by committing various kinds of fraud - like making up quotes and attributing them to the PM, or relying on obsolete government reports into factory conditions. Those conditions had long since been fixed by the government's factory acts, but Marx couldn't mention that without undermining his central thesis that democratic capitalism was in a death spiral and couldn't improve the workers conditions, so he pretended he was citing contemporary documents.

Nor have "landowners already destroyed the economy of the country". The UK economy is the fastest growing in Europe right now (of the rich nations), unemployment is at record lows despite a long term massive influx of immigrants: its economy is literally the opposite of destroyed. You're lying about the reality of the UK, whilst criticising others for being naive.

Shooting down your trad-Marx rhetoric with economic facts is easy so I'd like to focus primarily on this oft-cited belief:

Beyond a certain point massive inequalities are inherently politically unstable and almost guaranteed to result in a seismic social dislocation. This isn't even a moral point - it's simply empirical.

But it is a moral point. The people who perform "seismic social dislocation" in response to (perceived or actual) economic inequality have a long history of performing that dislocation by shooting peaceful people, stealing all their stuff, building forced labour camps, liquidating all their political opposition and then turning their countries into hellholes. The communists who did all these things absolutely deserve moral condemnation and their acts cannot simply be whitewashed away as some sort of mechanical inevitability, no more than someone could excuse the Nazis as some sort of mechanical inevitability given the inequalities imposed on Germany by the Treaty of Versaille.

Compare the fate of every country where your views have gained critical mass vs America. The latter is one of the world's most successful countries, if not the most. The others are all slowly recovery from absolute poverty, and recovering only because they finally turned their back on your Corbynite views.