Even under socialism, planning will be done collectively, and the role of the manager will be obsolete.
Let me explain.
In Capitalism, the manager will be developing workflow, task priorities, and internal marketing nudges. Their compensation is directly proportional to the performance of their team, based on how well they meet/exceed benchmarks/quotas.
In socialism, there will be central planning. Ownership is collective, meaning the team will directly have a stake in the success of the project/task. Their own compensation (monetary or otherwise) is directly related to the performance of themselves and their peers. So, how a team will organize their workflow, manage priorities, etc, will be up to the team.
The result is that they will outperform any capitalist manager, because not only do they have a personal stake in meeting the benchmarks/quotas, but they also have the most experience in performing the task. There will be advisors to give them tools and techniques, meaning the team will get management training.