You're massively unfair on the 1945 Attlee government. They were one of the greatest governments this country has ever had. And I say that as a Conservative with certain Thatcherite economic tendencies, even if I am a social liberal.
There were good reasons for the decision to build new steam locos after the war. They weren't in a position to transition to diesel, but they needed new rolling stock. I'm not sure if Beeching didn't cut too far. But predicting the future is hard.
Remember that they were a government who'd been through two World Wars and one Depression. They had different experiences and wanted to try and work the economy a different way. They also had to deal with horrendous war debts, damage at home, and a horrifically complicated international situation. So while creating the health service, they were actually increasing defence spending over what it had been pre-war as a percentage of GDP. Secretly building a nuclear bomb, preparing for the Cold War, dealing with the Berlin airlift. Also having to maintain rationing in Britain inorder to be able to afford to feed the Germans in the British Zone, who's economy had collapsed.
If they made some mistakes along the way, they did a fuck of a lot, in a short time. They got the NHS and social security model about right. It was later generations of politicians who failed to adapt them to changing times and society.
I broadly agree that central planning doesn't work. I'd say that politically it had to be tried in 1945, because of what had happened in the 20s and 30s. Politics often trumps economics. In the short term at least.