Dragons cost a lot of mana, so permanents that can discount them are vital to get onto the battlefield early
And unless youre playing against Dan Bock in Tokyo, there has never been a deck in Magics history that contained no legal targets for Thoughtseize
Any of those creatures that aren't tokens won't become tokens in this case
Here is an example of a pretty all-in Emrakul, the Promised End decklist: Creatures (12) 1 Dragonlord Silumgar 1 Den Protector 1 Nissa, Vastwood Seer 3 Hangarback Walker 4 Deathcap Cultivator 2 Emrakul, the Promised End Planeswalkers (4) Lands (23) Spells (21) Obviously Nahiri, the Harbinger is a natural fit for Emrakul, the Promised End, and Patrick Chapin wrote last week about a bunch of different versions of Emrakul, the Promised End decks, many of which included the Boros planeswalker
When we mixed ruby and amethyst for example, the deck felt much stronger compared to the other combinations