Yeah it used to be the big one, all the developers and big brands would come together all at once with big reveals and showcases, ESA itself is also partly to blame as the prices for booths started getting stupid in the latter years and smaller indie devs got priced out, and started doing their own reveals and showcases.
Once the big guns like Sony and Nintendo left to do their own thing it was pretty much doomed. The whole point was that everyone came together at once for a big expo, and you would get a big dump of new stuff to look forward to.