Well, WHY did they fail. I agree with you that all your proposed solutions look and feel good and should work. But they don't work if we have right-wing power structures alongside them. If they were that good, maybe people would like that solutions more than right-wing power structures? My take: they failed because they require people to be universally good and don't account for selfish people gaining power. Selfish people WILL gain power because otherwise they couldn't do things they want for themselves.
>> nationalising important industries and resources - all nationalised resources are being wasted away for political reasons sooner or later. I know this from practice
> That's not universally true.
Nothing is universally true, including this statement. I have seen successful nationalized companies. But typically they work for the people employed there, a working product is only "byproduct" of their working. They don't stand a chance with companies making products to make best product out there. Alas, most companies making products now optimise for money given to CxO's and shareholders, so they have crap product anyways. Both pure communism and capitalism are bad.
>> Unionisation - helped for a while
> I'm curious to know why you believe this though; is it just an assumption because we don't see many union shops these
No, it's because my father worked in companies with strong unions from unionization start to bankruptcy and he told me how it looked, I have talked with other people and did my own thinking about this. Sorry, but I can't remember all those stories now, typically it goes like with all assured working conditions, where you can't fire worst performers because they have good connections, so they drag your company down. This is typical downfall of all communist-like companies and systems. Working people just work and don't care about politics. Those who don't want to work, just care about politics, are voted in and from then on, they are only parasites. You can't get rid of them, because they hold positions of power. If working people try to remedy this, they are fired until there are too many parasites for workers and whole system collapses.
Democracies of course are not immune to this, but a little more resilient, because you can change those in position of power, until you vote in some scumbags which change the rules. Only education helps with that.