Also, once you create a channel in Discord you cannot get rid of it without destroying chat history.
With IRC, you just /part without disrupting other people and even then you can go back and read chat logs, nicely persisted on your local disc as text files.
This is true; the closest thing you can do is collapse the category that channels are in, and mute the ones you don't want to show up. Any new conversation in a channel will pop them out.
To have IRC-level feature parity, the deletion action should make the channel read-only, visible only to past participants and push it down on the channel list, preferably under a special archive category that is collapsed by default. This can of course be done manually, but especially the permissions part is tricky and it still allows other people to nuke your chat history retroactively.