Love it or hate it, Discord changed the chatting landscape. They're approaching 100 million active users and have inspired countless other chat clients and software like Matrix's Element, or Slack. They may not have built Rome here, but I'd argue that the best innovation just repositions pieces that are already on the table.
Discord is a small improvement on already existing ideas. The number of users has nothing to do with “innovation”. Unless of course you think toilet paper is “innovative” because it has more users than Discord.