Is Bitcoin network truly distributed without central authority? When a node joins the Bitcoin network it gets its info from either a preinstalled list, dns or irc. All of these 3 could potentially imply a central authority for who's on the network. Who exactly maintains them?
You can get your pre-installed lists from anyone you choose by any method you choose. There is absolutely no requirement to you get these lists in any particular way or from any particular authority.

If you wish, you can make your own list of bitcoin nodes you consider "valid". You can publish this list by a web page, by DNS, or by any other method you choose. Anyone who wants to can use your list, or not use your list, however they want. And Bitcoin will work just the same.

When someone follows an "authority" because that authority is convenient, I do not consider that centralization. As long as people are free to choose to follow a different authority, or just do it themselves, if at any time they no longer like what that authority is doing, that's not centralization in my view.

And, of course, none of this is relevant once you find a few bitcoin nodes to talk to. It only affects the initial bootstrapping process. You have the same issue with getting the bitcoin software in the first place. Is bitcoin not decentralized unless everyone writes their own implementation of the protocol? Or is it decentralized so long as people are free to if they wish?