Discord is centralized. Yes, and? We are not in the end state of Web3 yet. Web3 is nascent and new. And we have to use some of the existing infrastructure to bootstrap it. Just as the internet was bootstrapped by the Department of Defense (via ARPAnet). Ideally we transition to a decentralized chat service at some point (some communities do use Matrix or Status), but in the meantime, we can't let perfect be the enemy of good.

Now go back to what the previous article was saying about decentralized (/federated) systems being slower, and consider how Discord got more popular than Matrix despite coming out a bit later (so it's not a question of "transitioning" - why not picking Matrix (or XMPP/Jabber) right off the bat ?), and despite Matrix being clearly more aligned with the decentralization values supposedly espoused by the "web3" people ?

And let me guess, do these people also "build together" using the centralized and proprietary Github built on top (and now bought by Microsoft, who knows what they'll do of it now...) of the decentralized git ?