ahead of the curve?
Nintendo was struggling to bring as much firepower as Microsoft and Sony because none of the third parties had games on their systems aka, no trailers to be shown at their show.
Nintendo's own exclusive is not as showcatching as the other 2. For example, Sony can easily show 3-4 AAA titles any given year while Nintendo can only show either Zelda or Mario and then they are dry.
Feeling the above 2, knowing Nintendo, they probably choose to save a few bucks on the conference cost and do a direct instead. So they are still in the game and have some exposure but don't have to try so hard every year in a battle they never win.
It is just like how Microsoft doesnt announce console sales numbers and says they "focus" on user engagement instead.
Except people complain that Sony's 3-4 AAA titles are, in the last few years, the same ones we've known about for about 2-3 years. As much as people are excited for Spiderman, its been a headline game since E3 2016. The Last of Us 2 has been shown in the last 2 E3s. Death Stranding has been shown multiple times in 2-3 years and has yet to even show actual gameplay (unless you count this latest E3 trailer as such), no matter how trippy you think the trailers have become.
And with Nintendo, there's more than Mario and Zelda. We've seen it with Pokemon and Smash Bros. headlining this year's E3. Heck, Splatoon 2, not Mario nor Zelda, has been THE game in Japan as its still charting high in the sales charts in Japan while games like MHW and DQXI have had great first 3-5 weeks and then later fell off the charts. We'll eventually know more information about Fire Emblem Three Houses, Metroid Prime 4, Pokemon 2019, Daemon x Machina, SMT V, etc.