I wanna expect Nintendo stuff at TGA but honestly.... ever since 2017 their presence there has been a bit disappointing. 2018 was just joker in smash (no gameplay) and MUA3, and 2019 was just third party partnerships (NMH3, BB2). A far cry from Bayo 3, Bayo 1+ 2 revealed and BotW DLC trailer and shadowdrop. Even the year before that was better with the first showcase of BotW since that E3 in the form of a trailer and a gameplay demo.
Maybe it's because Reggie left and he had a good relationship with Geoff. Idk how Bowser and him get along. You'd think they'd INCREASE their first party reveal presence given how it's growing each year.
Eh. Don't think it makes sense to hang the "no gameplay" asterisk over the Joker reveal. It was a huge deal, perhaps one of the most well received and well integrated reveals of the night, and the lack of gameplay had no real bearing on that. It was a clever move to premiere a trailer like that promoting a crossover with a game that was being celebrated during the main show. The lack of gameplay, if anything, had to do with the timing. Also, the stream was peppered with continual Smash advertisements, counting down to the game's launch that evening. That show even had a live performance of Lifelight. It was all an extensive use of the show as a marketing vehicle. For one game, sure, but they threw their weight behind it.
And really, now that we're winding down on Nintendo's announcements for the year, it's clear that they didn't have that much else that could've premiered at TGAs in 2019. The biggest reveals seem to have been intended for their own 2020 E3 show or around TGS (like Monster Hunter), so many months removed from TGA. (This is excluding the Pokemon DLC, which I don't think ever would've been announced in a format other than a dedicated Direct.)
I think this year we'll see HW DLC with a BotW 2 teaser. They generally seem to know what material is best suited for the TGAs. Far cry from Cranky Kong days.