I participated in some online debates with some who called themselves democratic socialists. Once pressed they can admit to some bizarre theories.
The folks I debated argued that socialism did not succeed because it had never been tried. They claimed that every country that called itself socialistic wasn't really since they were dominated by an elite that governed for their own interests rather than the interests of the people. Their utopia would, of course, be different.
They sidestepped one of your objections, the lack of a useful algorthm, by postulating a government that would place the questions of allocating resources to a vote. If for example, a town had unemployed workers, then that town would vote on the type of capital investments to put these unemployed to work, ie, build a shoe factory or a communal farm. At this point they began to get bizarre admitting that most people really wouldn't want to be concerned with subjects such as this so they probably would prefer letting an elite make these types of decisions.
The most bizarre of their theories was that by a correct allocation of resources to real needs, no one would need to work more than 20 or so hours per week. They accomplished this by riding the world of capitalism and marketing since they felt that these only made the workers think they needed some things. That once this artificially created desires were purged from the world, most folks would be quite happy living in a high rise apartment building where the typical family lived in only a few hundred square feet. No need for cars either since we would all ride mass transit to our government appointed jobs.
The bottom line is that the government would tell what you wanted, when you wanted it, and how much of it you wanted. The education system would be geared to convincing you that living on less was best. While they maintained that all of this would be achieved democratically, they also maintained that there would be, at least temporarily, the need for force just in case your education wasn't truely effective in convincing you that the plans of the elites were notthe best.