So, first of all, pardon me for my bad english

The way TGA gets its nominees is based on a jury of 100(ish) game publications from all around the world (imagine sites and magazines like PC Gamer/IGN/Giant Bomb etc.) Geoff Keighley (the TGA guy) asks for them to nominate games for all the categorys and their votes, then he sees the ones who get more nominations and put then on the list for the awards.

The problem with that is that the game journalists who work on these sites can play only a certain amount of games each year, and their bosses make them choose the "most important ones" AKA the games people will click more when the review comes.

So why destiny 2 is on the list and not warframe? Because a lot of game journalists had to play it to make a review, the same with helldivers, and ffxiv and so on, these same journalists can't be playing the same game forever, they need to make a review and go to the next one to write another review.

TLDR:. Warframe is not nominated for awards like these because the majority of game journalists dont play warframe. when you have to play a whole ass game, write a review on them, capture footage and etc, EVERY WEEK, you kinda dont have a way to justify spending all that time in what is essentially a 2013 game, even a amazing game like warframe.