Technical innovation increases the productivity of labor in industry. If production shouldn't be wasteful, there needs to be a reduction in workers. Where do all these workers go if there's no unemployment? In a capitalist economy the workers are left to die on the streets but in a socialist economy they need to get a job again, right? Does the state take the burden of cost of reeducating these workers to enter another field and factor this into calculations when introducing new technology?
Depends on the situation.
If some new coal mining technology means there's now 50% of the available coal mining hours, it's plausible that all the existing coal miners have their hours cut by half(-ish) while still being paid the same. The transitory period would see some coal miners switch to poetry mining.
If a technology wipes out a type of job, e.g. computers (the women that did lots of maths), the transitory period would see more skills tooling, holidays old be paid out etc.
I think it has also been easier to find work in socialist states as well, less onus on the individual to maintain energy under years of rejection. You just kinda sign up for some job registries that state your intention to work in an industry.
Remember that the end of all this is communism; the technology of production has reduced the hours necessary so much that the needs of society can be provided by people who essentially do X task as a hobby (or, in another way, professions don't exist, you can try your hand at farming a couple of hours a week and produce enough food for your entire community).