Do you think they just decided on a whim to not include that stuff? Like, they were in a meeting and were "Ya know, fuck those Stallion and Artisan guys"?
Or maybe the player data showed those were the least played modes?
You're giving them too much credit.
This MP is bare bones, period. This data nonsense is dumb, because even after their 'peak' the other modes were populated and you could find a match. It's only years after they were released where you have trouble finding games on certain modes that are not TDM. Even now, you can still find matches of TDM quickly in UC2 and UC3.
Take Plunder. It worked and played well in the past two games, yet in 4, they completely ruined it for no reason whosoever. Or why not look at TLOU MP having a solo Playlist and this game lacking one. These uncessary changes and decisions just shows that there was something going on with the MP team for this game.
It plays well, it runs at 60fps, the gun play is amazing, but the game no matter how good these elements are will always lack content. This is what this game is missing still: content.
I am a dedicated player in the Uncharted MP games, where I play them years after everyone else has moved on to other MP titles and for me, it's such a disappointment at how everything was handled for this release. Missing modes, a repetitive experience with survival which was basically time trials (though at least arena will somehow fix this), no labs, no community events, hardly any XP/relic weekends, maps, missing characters from past games... It just makes you think wtf went wrong.
And this past stream... I don't even have words for it.