The core main characters in book 1:
Rand, Mat, Perrin, Egwene, Nynaeve, Morraine, Lan.
The core supporting characters in book 1:
Thom, Loial
You can also make an argument that the following characters were critical to introduce in book 1:
Min, Tam, Elaida, Bayle, Elayne, Galad, Gawin.
Meeting Rand was one of the core reasons Elaida performed the tower coup.
Instead, were got a lot of characters that did not matter for season 1 like Liandrin and Logain, and even Siun.
People argue that introducing Elayne in season 1 to have her wait around. Well, what about Logain. He does not become important until the coup and escape to Salidar while Elayne, Bayle, and Thom all had major roles in book 2.
They added a load of trash that never happened into season 1 while ignoring core characters and core supporting characters.