Why Do Eternals Have Such Imbalance Powers Among Themselves?

If the Eternals' main goal was to defend mankind from the Deviants, it's understandable that the Celestials didn't give them more powerful abilities. The Eternals arrived in MCU Phase 4 and delivered a significant boost in terms of power and in-universe chronology. Whereas extraterrestrial races like the Asgardians and the Kree appeared to be light years ahead of humanity in terms of physical prowess and technology, the Eternals are light years ahead of them. The Eternals are exalted beings that might easily take over the planet if they didn't obey the command to stay out of ordinary matters.
Modern society owes a large portion of its development to the Eternals in the Marvel Cinematic Universe, who used their skills to drive humanity ahead as the Celestial Tiamut grew in secret. Phastos, an Eternal with the capacity to develop high-tech innovations, was instrumental in this process, allowing the world to advance in terms of technology and scientific growth. Other Eternals, such as Ikaris and Gilgamesh, were given superhuman abilities such as flying and tremendous strength in order to keep the Deviants away if they ever appeared.
Some Eternals, however, were unable to offer as much as Phastos, Ikaris, or Gilgamesh. When battling with Sersi and Ikaris, for example, Sprite's illusions can only assist her to distract the Deviants for a brief time. Ajak's healing skills are useful for other Eternals, but she can't stand up against many Deviants, and she can't truly protect herself against Ikaris' betrayals. Druig's ability to influence minds makes him one of the most powerful Eternals, but he can only guide people away from danger because he doesn't appear to be able to mind-control the Deviants themselves. Furthermore, Druig is not permitted to directly influence humans, therefore his great abilities are mostly wasted. Given the nature of the Deviant danger, it seems strange that so many of the Celestials' powers are useless.
It's likely that the Celestials' ability to create the Eternals was limited by their own might, or that the Eternals' stable brains necessitated greater resources. After all, the Deviants, who came before the Eternals, lacked empathy and self-control but possessed a unique capacity to absorb and mix superpowers. The Celestials might have made the Eternals indestructible or given them all the powers they could imagine if their power was boundless. This is true in the comics, as each Eternal has the same set of abilities as the others. However, given how long it takes the Eternals to complete their mission, the Celestials are unlikely to be able to assist them much further.
For its live-action version, the Eternals had to be weakened. The suspension of disbelief would be difficult to sustain otherwise. Nonetheless, the Eternals' MCU abilities fall short of their objectives. Given how strong mortals like Captain Marvel, Scarlet Witch, Doctor Strange, and the Hulk may become in the Marvel Cinematic Universe, the Celestials' failure to produce an invincible species is unimpressive.