Sure, but then you see press coverage generated by a new trailer for a much anticipated game dropping on YouTube in 2018 like God of War, Spider-Man and RDR2, all of which got insane amounts of press coverage including in non-gaming media from new trailers or footage - and enjoyed coverage longer because of less competition.
I don't know how many podcasts you listen to, but the ones I ones I do paint a different story of E3 by the people who cover it. E3 is the equivalent of 3-4 months press coverage condensed into five days; what used to be three official press event days plus conferences that start on the weekend prior, but now it's down to two (IIRC) official press days. You're not getting good quality press coverage from E3, every site is simply regurgitating the same pre-prepared PR material. Interviews are staged or heavily managed by PR people. The press people are rushing about, frazzled.
Events like this, EGX, GamesCom are great for the public. I get along to EGX when I can.
That's a pretty big 'other than'. Anything somebody announces, unless it is earth-shattering, is going to be the centre of attention for anywhere between 60 seconds and maybe a few hours before something else is announced that garners everyone's attention and knocks your story down any gaming web page. The volume of coverage of E3 is also going to be more than casuals will consume. And casuals are by far the biggest number of portion gamers.
In Government Press Office, they refer to media days like E3 goods days to bury bad news because very people can keep up with it all. You just can't if you have a full time job or other full-time commitments, a family etc. It's too much.
I agree with a lot of your points, as well as iroboto's sentiments. However, I still feel Sony, Microsoft, Nintendo and many of the triple-A game Publishers/Developers (e.g., EA, UBI, Activision, Bethesda, etc.) aren't necessarily hurting themselves by missing one or more E3 events in favor of their own specialized events. Look at how well (well being an understatement) Rockstar does without [ignitial] E3 exposure when announcing titles. Gaming companies whom are well established can pretty much carry their own weight (i.e., hype, branding, self-promotion, etc.) without necessarily needing an event like E3. I also believe more smaller independent companies can benefit more from E3 without being vastly overshadowed by the major players within the gaming industry. And possibly receiving more exposure (if their wares are impressive) from such specialized events held by Sony, Microsoft or Nintendo.