[KetoManx64]

The exchanges and miners do have a large influence, but the node runners (the users) have a voice as well. The node runners can get together, and refuse to peopogate the blocks of of the miners/exchanges that are being bad actors (BIP 148 for example) and also (BIP 110) that's currently making the rounds.

If a large enough percentage of the node runners need refuses to propogate a block from a bad actor, then another miner can mine the same block and get the reward.

[stymaar]

The miners don't need “node runners” to get access to other miners mined block. That's not how the bitcoin protocol works at all.

In an ideal world the best non-miners can do is prevent some transactions by preventing them to reach the mempool, but you're not going to block an exchange this way either.

The bitcoin protocol is actually very friendly to centralization, the only mechanism that was supposed to prevent it was the PoW, which failed because ASICs exist. And as a result, in practice it's been very centralized for more than a decade now.