anyone in IRC chat can still record everything just fine
I addressed this. Yes, someone can invite a bot in a channel they control and the channel operators can kick/ban a bot. Also people can achieve E2EE encryption using OTR. So in fact there are two layers of encryption, one of which individuals control and the IRC admin has no visibility into. There is an unsupported OTR custom client for Discord but it is against the terms of service.
Discord on the other hand has visibility into everything and no way for users to know this. Anything said on Discord in text or voice is a permanent transcription record. People are made to believe they can delete messages, but they are just flagged as deleted in Cassandra.
If I want a private voice conversation with someone or a group, I invite them to my private uMurmur server. There are clients for workstations and cell phones. Some people won't use such things and those are not people I would likely ever talk to anyway.
Transit encryption maybe, but admins can still read everything.