The comment above says: "In the UK Labour has advanced, and even in the US the Sanders campaign provided a platform for Left renewal."
These are sheer illusions.
The US Democrat Bernie Sanders stands for import controls - which the trade-war mongering Trump administration would heartily agree with. Jeremy Corbyn in the UK is in the long line of Labour "lefts" - Wilson, Benn, Foot etc - who are parliamentary careerist frauds down to their little red cotton socks. His "anti-austerity" promises are both totally empty and impossible to fulfil. In government, if he gets there, his exposure would be completed by the banks clamping down on him and shallow "leftism" in the same way that Greece's Syriza government was squelched.
The world is deep into global monopoly-capitalist "over-production" crisis where the system is clogged up with decades-worth of surplus capital and, as Marx explained, there is a shutting down of the economic system, an astonishing outbreak of "poverty in the midst of plenty" (see Marx's Capital Vol 3 on crisis).
The crisis broke into a financial earthquake in 2008, and total meltdown has only been staved off by insane amounts of credit creation, called Quantitative Easing, putting generations of taxpayers in hock.
Businesses have been going under all over the world; states and governments all over the capitalist world have been forced to cut public spending more and more sharply, hitting jobs, pensions, healthcare and all services.
The political turmoil is so intense that Establishment parties have been getting a more and more hostile reaction from their publics. In general, they are hated and despised as corrupt crooks - and this is totally correct.
None of the "lefts" had "glory days". Any of the previous "great reforms" they brought in (NHS in the UK, etc) were only ever permitted by the capitalist ruling classes out of fear of socialist revolution. Reforms, even when useful to workers, have only ever also soaped the rope for workers by putting them off the need for revolution to end capitalist class rule and the danger of renewed world war, after two previous horrific rounds of mass global slaughter.
The reason the Italian "lefts" have such derisory support is because they richly deserve it. None of them are clear Leninist parties expressing the need for revolution, and with some sort of worthwhile track record in explaining the crisis realities of capitalism and need for workers states of proletarian dictatorship to see off any attempted counter-revolution.
Mostly, as with M5S, any "leftism" is a mix of pacifism, pleadings for fairness from the capitalist exploiters (what a sick joke) and an obsession with populist, single-issue politics (around environmentalism, gay rights, feminism, etc) that completely keeps them in thrall to middle-class public opinion. M5S is so confused and middle-class, for example, that it panders to the right-wing over the refugee crisis (which can in fact only be handled by world revolution and defeat for imperialism, so that people can live safely and happily in their own countries).
None of the fake "lefts" would in practice say boo to a capitalist goose; with them, there is just the mirror-image uselessness of Trot anti-communists who hate the history of the USSR and Eastern Europe more than the CIA, versus the museum-Stalinist idiocies of revisionist groups who refuse to recognise that it was the retreats from Lenin's revolutionary understanding, started by Stalin, that lulled everybody into reformist complacency in the Europeans CPs and eventually liquidated the USSR, just to show what peaceful, inoffensive pussycats they were - which resulted in mass economic collapse, and capitalist carpet-bagging and NATO Nazism storming right up to the borders of prostitute, gangster, oligarch-riddled Russia.
It is completely fitting that a movement started by a clown (Beppo) should be where it is in ludicrously unstable Italian politics. Certainly, the mushrooming of stinking fascist nonsense in Italy, Europe and the USA (Trump is very like Mussolini with his deluded "Make America Great Again" bombast and tub-thumping warmongering) is a sign that workers should get ready to fight.
But what and how?
Support parliamentary democracy and class collaboration, which is the permanent practice of shallow "leftism"? To make "reforms" that cannot be implemented in slump-ravaged economies, and which the imperialist-controlled banking system would never permit?
Or fight for the socialist revolution to end capitalist exploitation and war for good? Which means building parties of Leninist theory, like Lenin's Bolsheviks - or maybe even fiercer and better.
Given the appalling state of political shallowness on the planet (with even the Cuban CP joining in dull-witted "condemnations of terror" as if the peoples of the Middle East and Third World had absolutely no right at all to fight back against the endless bombing and destruction of their countries by US and Western imperialism) this could take a little while.
But debates are breaking out. And e-Flux is helping that debate by being an excellent online platform for such discussion.
Build Leninism. See epsr.org.uk