I feel like we mostly agree with each other, we just don't agree about the extent to which FOSS is helpful.

I agree, although perhaps less dramatically, that closed source is harmful, and that you can't trust it. I agree that FOSS makes trusting software easier (although not trivial, critical vulns can still exist for years), and FOSS helps democratize whatever the software is used for (although in the current capitalist hellscape, software tooling is a relatively small hurdle).

To me, you don't need FOSS to build a (literal) guillotine, and you don't need FOSS to spread flyers. It's not necessary for a revolution, and recent history seems to show it doesn't really move us closer to a revolution. I don't understand the basis for your claims otherwise. Communication benefits from software, and FOSS means that we can trust our tools of communication more, but in the end we still largely depend on ISPs and corporate hardware. People don't have open source hardware phones, running mobile distros of Linux, loaded with radical app repos, running a massive adhoc p2p communication network.

I see FOSS as a goal. I want to live in a world where FOSS is the natural state of things, collaborating instead of competing. That is the end state I want to achieve, but it is not itself the solution for achieving that state.

FOSS is the solution (in microcosm) in the sense that it is a good replacement for capitalism, but not the solution in the sense of doing the work to achieve the end goal.