Why do the Egis appearance look awful and unimpressive

[Kiroh]

Uh...you need to pay attention to the story better, The Amal'ja Had been stealing shipments of crystals and kidnapping people prior to that in order to summon Ifrit, we just happened to be there at the culmination of their efforts, same goes for the Summoning of Titan, they also draw upon the collective belief of all their tempered thralls, not just the one doing the summoning.

During Garuda's story, outside of their respective homelands, with only 3, average beastmen and zero crystals they were summoned full sized and full bodied.

Pay attention to the story before telling other people to pay attention to the story.