My issues with Ajak and Gilgamesh was they died......that was the main issue for me. Sprite did nothing for me at all. Druig was a bit too brooding and we've seen that too many times already in the MCU. Phastos was fine, I wished he had more to do and his son is a bit over the top. Ikarus, Thena and Sersi, while not great, were not terrible. I thought the characters in here were much better than the characters in Thor the Dark World but the characters in that Thor movie have since became more likeable. The use of the villains was the same in both movies. I did enjoy the power sets of the Eternals though, quite different than what we have seen in the MCU so far.
I enjoyed Black Widow, and I liked the characters better than I did with the Eternals, so much so I want to see more of Alexei, Melina and Yelena, especially Yelena. With the Eternals, I don't know if I want to see Ikarus, Sersi, Thena or Druig again. With Shang Chi, I want to see more of Shang Chi and Katy (although I don't want Katy to be an Avenger, more like an ally to the Avengers). I wouldn't mind seeing Xialing and Ying Nan again. My top characters in the Eternals were Makkari, Kingo and Dane Whitman, despite the little screen time he had. I would be open to seeing Phastos again.
The introduction of Pip the Troll and Eros was fine I had no issues with it. My issue was the Dane Whitman post credits. Why would you only hear Blade and not see him? That makes no sense since he's a new character. I had no issues with Shang Chi and Katy interacting with Bruce Banner and Carol Danvers in hologram form because we know these characters and not having them in the flesh is not a big deal. If the off screen voice had been Dr. Strange or Wong and that was it, it would not be an issue as we know these characters. We don't know Blade. It made no sense.