I always enjoyed watching videos of crowd reactions to trailers. It's a bummer we won't get those anymore, but I can see why it's too expensive to host an IRL event. I wonder why they didn't transition to an online-only expo? I'd watch that.
E3, kinda makes sense for connections and getting boots on grounds and showing stuff in progress in controlled environment. But for online you are better off going alone, unless you are tiny.
Today Geoff Keighley's Video Game Awards basically took over that role and similarly is the single biggest stage/audience to announce a new game to. If you had a game that they were interested in revealing + you thought it would sparkle to its audience it's a powerful platform.
Most industries have trade and consumer shows (from film to boardgames to concrete). There's no reason to expect that gaming is somehow unique and should not have one. It's unlikely it will be like the E3 of decades past (or even have the name), but there's value to getting consumers to see/try a bunch of new games.