Agreed. I think the root of any issues with it was that it covers masses of ground too thinly that built no explanations or reasons to care.
Theena was completely bemusing. What the fuck was that "madwiri" thing they were talking about where she goes super-fighty at everything around her? Completely unexplained and arbitrary. And they had her down as a legendary warrior. How? When? How does that fit into their existence or matter in the story?
Thena did feel a bit underutilized and it felt like her only purpose was to introduce Mahd Wy'ry as a way of explaining their existence (of being artificial beings that have their memories wiped between Emergences). But yeah, I agree, they really didn't show us how she was a legendary warrior, only that we were told it. other than the 2 or 3 fight scenes she was showing off. In a long-form series, we could've gotten an episode focusing on her and Gilgamesh and it would've been really nice to learn more about them, individually and together. But I'd say Mahd Wy'ry was sufficiently explained by Ajak and then later on in the film once we figure out that their memories are tampered with by Arishem after every mission/Emergence.
I hated Sprite as a character. Made no sense that she was stuck in a child body. And Kingo/Gilgamesh were essentially the same except power was either fixed in the fists or as shooty-balls. Meh. And Kingo seemed to be a totally self-centred idiot.
Well I'd say Sprite was the way she was just to have a more diverse group of Eternals and as a way to have someone younger in the group that could easily identify with younger natives of any planet they are sent to. She is meant to represent a young, playful trickster type, thus her illusion casting powers. As for Kingo, he's the comic relief that you either love or hate, as I see folks really like him or just despise him, and comic relief characters are usually written that way anyway.
Ajak's super power seemed to be that she loved the others.
Ajak was the mother of the group, metaphorically speaking, but she was also their healer. We see this in their arrival on Earth when she is healing Ikaris after their first battle. And when the Deviant Cro took her life force, it gave him her healing ability, which we see when it attacks Sersi and Sprite in London, although upon first watch it's difficult to make that connection. When you know Cro has already killed Ajak by that point on a rewatch, it's pretty obvious that he's using Ajak's power, especially when Sprite realizes it was healing itself and that they never used to do that before.
A longer series could have shown much more of their 7000 years spent on earth and filled in background on the Eternals (and Deviants) where it was missing so it made sense.
Edit: Maybe the source story just isn't very good and they needed to have diverged from the source material more.
I think the last time Marvel let a film idea turn into a series, the series didn't work out too well (Inhumans, although that wasn't technically under Marvel Studios/Kevin Feige), and I'm sure Marvel wanted a big budget film for this first outing of the Eternals. I would not be surprised if the next time we see them all isn't on a limited Disney+ series, but even if we get a second film, the team is now smaller without Ajak, Ikaris, and Gilgamesh, though we now have Starfox/Eros joining the crew of the Domo on their search for Sersi/Phastos/Kingo, so who knows. If it's an entirely space-faring sequel, we may not even see Sprite since she stayed on Earth and ended up becoming mortal anyway. A smaller cast with a tigher story would greatly benefit the sequel, but it'll be at least 2024 before a sequel happens, probably even 2025, since this year and next year are all packed with previously announced films, and the film dates earmarked for 2024 will probably fall to other projects that haven't been given dates yet (Fantastic Four, Blade, Captain America 4, Deadpool 3, and a film about Mutants).
-Marc.