(arguably it was never really successful. I'll reference Bill Hicks for that)
"Now I'm no bleeding heart, okay? But, when you're walking
down the streets of New York City and you're stepping over
a guy on the sidewalk who, I don't know, might be dead...
does it ever occur to you to think 'Wow, maybe our system
doesn't work?' Does that thought ever bubble up out of you?"
The guy on the sidewalk will be there regardless of the economic system, because with few exceptions the homeless aren't homeless because of economic reasons. Nearly all of them are where they are because of various forms of mental illness, and the fix for that isn't dumping capitalism, it's reinstating the system of state hospitals to care for the mentally ill, treating them to the degree we know how, and just keeping them reasonably comfortable where we don't. Of course, we need the hospitals to be much, much better than they were; the reason they were largely shut down is because they were houses of horror and it was easier for activists in the 70s to get courts to shut them down and put the patients on the street than to actually get them cleaned up.
Not coincidentally, those hospitals also used to hold a fair number of people who are still in state care, but at much higher cost because they're in prison.
I will grant that state hospitals and similar systems are socialist, so to that extent perhaps socialism is the solution to the guy on the sidewalk. That doesn't mean socialism is the right answer for those who aren't mentally ill.
With respect to people whose jobs are automated away, IMO the right level of socialism isn't to give them a basic living stipend, but instead to help retrain. One thing that most people worried about automation removing jobs don't consider is that the cost reductions due to automation go primarily to reduce the cost of goods, and therefore to lower the cost of living and raising the standard of living, which opens up all sorts of new opportunities for work, in two ways. First, by lowering the cost of living, the disposable income of the (working) masses increases and they start buying services that were previously out of reach, thereby increasing the demand for -- and jobs in -- those services. For example, in the 18th century there were very, very few professional hairdressers. In the latter half of the 20th century it became a very common profession.
Second, the lowered cost of living opens up possibilities for living doing work whose value previously simply wasn't sufficient to support life. It's not often that we think about cost of living decreasing. It seems like it's always going up, but that's because we measure it with devaluing currency, and because our standard of what constitutes an adequate lifestyle is constantly increasing. If instead we fix a particular standard of living and then look at how much time must be put in to earn it, the cost of living has been on a long downward slide for centuries, and automation is going to accelerate that.
I'm not saying that everyone is going to be a hairdresser, and I have no idea what all of the jobs of the future will be. I think the major growth will be in the service sector, because people do like receiving service from people not machines, no matter how competent the machines become. It wouldn't surprise me if the biggest growth areas are all around non-essentials, like art and entertainment. What I am certain of, though, is that as long as people have disposable income they will find things to spend that money on, and that will involve paying other people for goods and services. Many of those goods and services will seem ridiculous fripperies to us today, but much of what we spend our money on today would seem silly to people 100 years ago.
Oh, one other thing I'm certain of: people need to feel that they're earning their own way. Life earned is better than life given, regardless of how it is earned. Welfare is a fast road to unhappy dependency. That's not to say that providing short-term support to people who are transitioning isn't a good idea, but long-term unearned subsistence is a recipe for angry, unhappy people.