They don't try to be entirely decentralized. Or entirely centralized. They balance between both. DNS still requires registrars and root servers if you want the

They don't try to be entirely decentralized. Or entirely centralized. They balance between both. DNS still requires registrars and root servers if you want the whole world to be able to find you, but works just fine as well without those bits if you are fine with having a smaller community and can run a private root. Ultimately I tend to think societies do best when the forces of aggregation and disaggregation can balance each other out and optimise for each other's strengths and weaknesses.