> Apparently those options are not good enough to be implemented.
These options have actively been opposed by those in power, because left wing politics weaken their power. Case in point, all those coups backed by the US government against left-wing governments.
> Unionisation - helped for a while, then those companies where it was implemented didn't survive because they could not make anything effectively.
Not true - Hollywood is heavily unionised to this day. I'm curious to know why you believe this though; is it just an assumption because we don't see many union shops these days, or do you have other reasons to believe this? Because there are other reasons to credit for the lack of unions nowadays, namely anti-union propaganda and deliberate weakening of unions by neoliberal politicians (which is basically all of them nowadays, but Reagan and Thatcher are the classic anti-union tag team).
> - building a cooperative-based economy - would be nice in theory if all people could cooperate. But in reality, they do not, there will be freewheelers who game the system.
That's not what a cooperative economy is. A cooperative economy is an economy based in cooperatives; basically a company but owned by the people who work there.
> UBI - not tried yet is the only difference between UBI and communism
At least we're in agreement that UBI could be good. Love the 'real communism has never been tried' reference though.
> minimum wages - we have minimum wages in Poland, they don't help that much, but weren't updated and inflation eaten them away.
Yes, minimum wages should be pegged to standards of living. Otherwise politicians intentionally don't update them so they become redundant.
> 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. They're certainly trying to disassemble nationalised healthcare here in the UK, but it's usually done by right-wing politicians who are anti-nationalisation anyway.
> building systems of mutual aid - that helps, but if nationalised - they are squandered for political reasons. If commercial - being squandered due to greed. But yes, they are mostly working in most countries.
Mutual aid is community networks of people who help each other out, not a national or economic political project.
I do understand the skepticism around leftist politics - after all, many have failed under pressure from right-wing power structures. Some have devolved into worse systems than the ones they opposed (though it's important to point out that libertarian socialists and anarchists opposed the USSR right from the beginning). But don't assume that because leftism is not currently winning, it's because it's inherently flawed, rather than facing a stronger opponent that must be overcome.