Socialism means workers collectively own the means of production, and it isn’t synonymous with central planning. Concepts like ParEcon, Worker Councils, Mutual Aid, and so forth reinforce this decentralized structure.
Capitalism is similarly not a system of decentralization but of many centralized islands. Each individual capitalist entity is very centralized in structure, more so than a system of Socialist entities, such as Syndicalism or Market Socialism.
FOSS itself rejects the profit motive and markets, and therefore is the antithesis of capitalism. Capitalism relies on private ownership, the profit motive, and IP protections, all of which FOSS abolishes.
Truthfully, the fact that you don’t want some CEO or bureaucrat deciding what gets produced unilaterally is precisely why your views are actually that of a leftist. You desire more democratization of production, a Socialist ideal to the core!
The fact that FOSS is based on non-profit decentralization is the very reason FOSS communities are dominated by leftists.