In my opinion, running a full node without securing the network is a very expensive choice with the least benefit.
I disagree, but as you've pointed out, that's a matter of opinion.
It'd be better to simply discuss with other people in this forum; that'd be more beneficial to everyone.
I'm not sure that I agree that it's "better", but I did offer that as one of the ways to participate. See here:
4. Participate in discussions (both online and in your daily life) about bitcoin and educate others about how bitcoin works and what its benefits are.
Dialogue is democracy.
Democracy requires more than dialogue. Regardless, Bitcoin is not a democratic system, it is a consensus system.
You seem to think that miners have all the power in the Bitcoin system. The only power that miners have is the power to choose the order of the transactions in a block. They do not enforce the consensus. The nodes do. If a miner creates a block that fails to honor the consensus rules, every node in the entire world will reject it regardless of the amount of hash power that miner has. The miners do not have the ability to implement any change that would violate the current consensus rules unless they have the support of the nodes.