It's a walled-garden system which is fine for private chats between groups of friends, but Discord is increasingly being used as a place to report bugs and share information. Telegram furthermore requires signing up with a phone number which Discord did not (now, often, you need to for participating when an admin of a community aka gild aka misnomer "server" turned on that requirement)

https://xkcd.com/979/ This comic will not be understood by gamers growing up today... (Except in many cases someone posted a solution or nudged DenverCoder9 in the right direction at least; with Discord, Slack, or Telegram you'd simply never find the thread in a search engine to begin with.)