To answer the question in terms of things you personally can do, I think the boring and realistic answer is to research organizations who align with your goals and who you think have effective methods, and get involved with them.
Personally I like represent.us - They’re specific to the US, but their idea is to put anti-corruption laws into place that help remove the influence of money on the government. This would help get laws passed that favor everybody instead of just the rich. Their approach is to begin at the local level and get enough momentum for a national movement to have some power.
Here are a couple of videos they made, first about what the problem is, and second about how they are trying to solve it:
I think it’s a valid thing to consider. Due to the nature of the fediverse, there will always be small instances. I guess you could say their purpose is to allow Lemmy to be decentralized.