Non-spoiler and TLDR version :
Average film as not a bad or a good film. Given the film setting and plot points, I understand why it didn't really execute that well. Given the gravity of this film on the new MCU franchise, it was quite underwhelming. No real character arcs except for Ikarus, and no justification for why some character chooses A over B. Felt like it was trying to do a lot of things at once, which just made the film feel diluted. Plot points were good but were underdeveloped. Good performance by the cast and beautiful cinematography.
Spoiler discussions (DO NOT scroll down if you haven't seen the movie) :
Criticisms:
Because of how the storyline was set, some of the character arcs and developments hold no real gravity towards the audience. Death of Ajak (Salma Hayek's character) didn't feel much since we didn't get to spend much time with her. Insufficient development on most characters which didn't allow us to see why some character behaves and the reason of their choices. Example 1: Why Ikarus wasn't able to shaken his belief in the Celestial's. Example 2: why Sprite chose to shank Sersi (her best pal over Ikarus) and then her core character issue only to be shaken off later easily. Others were pretty much a sideshow which I understand given the time it would've took. Even with a major character defining moment of Ikarus choosing love for Sersi over loyalty towards Celestials in the end, his suicide (although was poetic) just undercuts the message.
The plot twist of both the Eternals and Deviants both being just pawns in a game held no real weight was it was literally thrown halfway into the movie when we were just learning about the Eternals purpose at the start. The Deviants ability to gain sentience plot point was pretty much used only to "help Thena remember?". BTW, they mentally incapacitated Thena which didn't help anyone, nor serve any hidden purpose to the Celestials. It felt like they introduced a badass character only just to cut her out to increase the tension in fight scenes.
Praises:
Superb performance by the cast which they exhibit and deliver each line with great emotion that really tried to connect with the audience, even with a severely limited context and time we were exposed to the characters. Cinematography and CGI was on point. Can't complain about the extensive use of CGI fights since they are advanced super aliens (robots). Some philisophical dabbling was great but because of the time constraints it wasn't fully utilised.
Also, I'm really glad they really did the "Show, don't tell" which they subtly pushed messages instead of shoving it down our throats, unlike some other movies. It would've otherwise felt like a lecture rather than an entertaining movie. Show the diversity without making it a glaringly large issue is way better, despite the film was originally marketed that way.
Conclusion:
IMO felt like many things could've been fixed if they could've just chilled out and not crammed so many plot points into a single movie. Should've made the origin story about fighting the Deviants perhaps in the ancient past (as they learned about their ability to gain sentience) which sows some doubt about their true motives. We don't really need another MCU film set in modern times, since really they were an ancient and immortal beings. This would've allowed more time to flesh out each character (with their own arcs) and allow us to see why they behave as they are and bond with them. Then the true reveal of the Celestial's plan can hold more gravity in the second movie. Tbh tho this then would've made for a good third finale.