Heartless Summoning is my personal pet card for big-dumb-creature typal decks, and I wouldnt hesitate to put it in the command zone if I could
Flicker decks are indeed looking exciting, and although Tricksters Talisman makes tokens, Id still say those are the sorts of decks that want to take advantage of it: decks with lots of powerful ETBs
Sacrifice this artifact at the beginning of the next end step
At the end of the day, when you're getting a free, massive dinosaur every turn it's hard not to win games
I also feel that Genesis Ultimatum has no Red either, it draws and puts permanents into play so it's Blue and Green
Aside from cards on the Banned List, this category has no deckbuilding restrictions, so you can feel free to build around early-game combos and mass land denial and include as many Game Changers as you want