Why socialism doesn't work: Because it has so far required a revolution, often forced upon an unwilling populace, to come about. And who rises into power in a violent revolution? It won't be the people who actually care about the people and want to implement the best possible system, it is ruthless people who love power more than anything and implement a system that gives them more power rather than a system that could maybe work, and the people don't matter. I don't know if democratic socialism would work, but by definition it would have the people's support, and that alone would give it far better chances of working than any system before it.

Meanwhile, "socialism" like social democracy, including things like universal healthcare, easily affordable education, progressive taxation, seems to work quite well in Northern Europe, for example.

As a side note, I feel some American conservatives are being intellectually very dishonest when they claim that Venezuela proves that "socialism" doesn't work and therefore USA shouldn't have universal single-payer healthcare. You don't need to go all the way to socialist communism to have universal healthcare, which is obvious when you look at any country that already has universal healthcare. High taxes on rich people isn't Venezuelan socialism either, because you could have a hardcore capitalist society that just happens to have strong taxation. You can mix aspects from different systems to find a system that works best instead of accepting one bulk package of a system.

Remember, you should steelman your opponent, not strawman them.