Decentralized means there is no single point of authority. This is given. The definition doesn't say anything about everyone having exactly the same say. By your definition Bitcoin isn't decentralized, as the biggest miners could change the protocol and everyone else's more would be running on a fork.

Everyone can run a node, everyone can be a witness. Like with every other coin, getting to produce a big amount of blocks requires a big investment.

And people don't become whales over night, or in a month. How many new whales have been created in the months before? That measure is useless.

And for the last part, there are rewards on medium for successful authors.