The normal critique of socialized medicine is to point out that people have to wait a long time for these kinds of treatments in places like Britain. And that's certainly a valid critique. I'm sure my mom and daughter would still be waiting for their treatments, while my father and wife would probably be dead.
The key point, though, is that these treatments didn't just come out out of the blue. They were developed by drug companies and device makers who thought they had a good market for things that would make people feel better.
But under a national healthcare plan, the "market" will consist of whatever the bureaucrats are willing to buy. That means treatment for politically stylish diseases will get some money, but otherwise the main concern will be cost-control. More treatments, to bureaucrats, mean more costs.