The show's problem is there aren't a lot of merchandisable characters. I saw a website questioning how the hell we got Ghost Rider ahead of actual main characters like Daisy, Mockingbird, May or Fitz, and it seemed really obvious to me. Most of the main characters are just regular people in regular people clothing or if you're lucky, generic spy gear. Ghost Rider is arguably the only protagonist who actually has a cool superhero design that justifies making a toy of.
True but it is Shield so basically they are similar to Black Widow in outfit design. If they were in a big budget movie they would get made (Coulson, Hill, etc) but the TV audience is a bit smaller so all we get is GR in a limited run.
And who knows they could still get made