I really encourage you to spend some time in a youth community if you can't come up with answers to theses questions. The answer is, you don't. You pitched the thing already in a group chat. People either reacted with dozens of emoji and filled reply threads with "let's talk about this..." or they didn't and your pitch died on the vine. In more formal environments, pitches are usually in an RFC-like format and feedback is via comments on that doc (or Github issue, bug tracker, whatever-they-have-in-Jira)

Speaking persuasively in a one-on-one Discord video chat is identical to in person, or it is for people who don't feel awkward on video chat to begin with.

The design discussion thing, where the back and forth is purely technical, again just doesn't happen in video conferences. Meetings themselves were a shit format for this as well, all of this is done in dedicated group chats (Discord/Slack/Teams/whatever) where people can reference and link documentation readily and on their own time. Schedules are managed via shared calendars. Private discussions are taken to DMs.

Traditional conference-type meetings are for very specific topics, typically emergencies or something happening in real time where the pace of events lends value to being able to shout something quickly into a mic. Basically the same reason video games use voice chat. Sometimes there will be a monthly touch-base or whatever but I saw a lot of those get phased out during the pandemic because people realized that nothing new was getting put out over them.

One-sided teleconferences, where you're just dialing in to listen to a presentation of something and maybe a little Q&A, work identically to someone standing at the front of an auditorium giving a presentation. I present in a similar format weekly as part of a training program and the only difference is I get to sit down instead of standing at a podium.

All that said, I've been in a video chat with a dozen recent grads and they didn't slow down for a beat or appear to have an trouble reading one another. I cannot emphasize enough that you and I struggling with this doesn't mean anything was lost, just that we're getting older and the world keeps on spinning.

As a simple example, look at the protocol for half-duplex radio channels. One says something short and then says, "over" to signal that it's the other person's turn. Is this different than how people talk in person? Sure. Does it work? Definitely.

In your shoes, I would reexamine my concept of "design discussion". My team has made plenty of design choices during the pandemic. Maybe "pitch something" and "speak persuasively" is the wrong approach now.