Yes.
>Also relevant, do you need to be in all of them?
Yes.
You must be new here, because if you aren't connected to dozens of servers and idling in hundreds of channels (you only speak in maybe two or three of them) you aren't IRCing right.
What? I'm a confused old clod because we're talking about Discord in the year of our lord 2024? Same thing, it's a massive textual chat network based on a server-channel hub-spoke architecture at its core.
What is actually worth our time asking is why we could do all that and more with no problems in the 80s and 90s using hardware a thousandth or less as powerful as what we have today.