> so even if you see a conversation from a few hours ago, you can't participate in it.

Mirrored the limitations one would have in-person (i.e., they might have heard about the conversation, but now cannot participate in it, notably because it already occurred and all the same people may not be available -- you would have to start anew!)

Another interesting component of IRC is the explicit nature of people joining a channel -- it was treated the same way someone walked into a physical room; People would greet them and numerous conversations would naturally begin just by the essence of that presence. This is all mostly lost in modern clients.