@Fifteentoes I agree with you that certain "socialist" principles work at large scales, which is why even those who favour more libertarian or free market principles see the value of a lean state to oversee things that can be done at scale. Your NHS example could fit there.
But the problem with socialism at such a large scale is that it relies heavily on people seeing the collective good because they are happy to. Everyone paying according to what they have, everyone contributing according to what they can, everyone taking according to what they need.
What we end up with is things that work great in spirit but have dire consequences in reality.
Tax credits for example - everyone taking according to what they need. This fails spectacularly when our free market economy is set up so that wages will rise when people stop doing those jobs. It never happens because people in receipt of tax credits are topped up, people who come from other countries can send "shit wages" home and support entire families, and the people who suffer are those who still need the jobs but don't have any of these advantages.
Council housing are another example. When you are paying 1/2 the market rate, you can probably survive better on minimum wage when your rent is £400 compared to someone who can't find anything cheaper than £1200 a month. There is no "taking according to need" principle because you don't pass it on to someone who needs it more when your circumstances change.
I could give you literally 100s of examples of how government intervention either gets in the way of the free market capitalism we're supposed to be allowing to run our economy, fucking things up and ultimately making it worse and creating unfairness. The covid contracts are one, the Scottish land "carbon offset" is another, furlough is another, even this £400 "gift" - all of which is just our taxes btw - are all just in the last year or so.
With 68 million people in your "collective community" all it does is divide us. People get frustrated, then they get angry, then they start to think fuck the rest, I'd probably do better if I just focused on me because I'd be alright. You cannot hold the people implementing this to account when they are at the opposite end of the country and you are just one of 68 million.
When your "collective community" is in the hundreds or thousands, or even tens of thousands, people are far more willing to subscribe to the idea of socialism where those who can, do, and those who can't are supported because you care about your community. This is without going into how much easier it is to hold leadership accountable. The community knows you're only giving that contract to that brand new business because he's your brother-in-law, and the community knows where you live, and the community is close enough to take action.
There is really nothing new here, it's the way humans have operated for almost the entire time we have been human.
Of course things are better in so many ways now (the NHS and technological advancements being just two of them) but there is no real reason we need to throw all of those things away. What we should be doing is keeping what works for us, the people, and throwing away the rest.