Shatner is an RSC trained actor.Ok I do love William Shatner - but calling him an A actor could be a stretch. He does have a charisma factor - but I would bet Patrick Stewart and Jason Isaacs were getting "A"s in acting class - and William Shatners best bet for getting an "A" would have been sleeping with the teacher.
Point is, whatever you thought of him, the man performed well enough that his character was engaging and became a cultural icon. You cannot say that about Martin-Green. She lacks the powerful lead actor quality that past Trek leads have had. For her sake I desperately hope she finds it, but she totally lacks gravitas for me. That’s why I mentioned names like Viola Davis. The role needed talent.