What was the deal with Ego? Some questions:
Ego explicitly made a human body* for himself to travel the galaxy in, a part of himself that could travel and plant his seeds on each planet. A human, for some reason. Not a sequence of different bodies, a human for earth, a human for Nova Prime, a human for the Kree homeworld, etc. Weird.
Said human romances females on all of these worlds and has hundreds (thousands) of babies. None of these babies before Quill carry his Celestial gene (let's not geek into how Celestials in the comics are very different than Ego and not at all the same) and can help him with his expansion project. None of them? Maybe the trick was you had to match your form (human) to the target species. Or maybe that was an incredible coincidence.
So for the 'Ego on Earth' (and everywhere else) they de-aged Kurt Russell. How does aging work for the avatar of an eternal being? What I mean is, shouldn't we have a young Kurt Russell for the entire movie? Was Quill also his last attempt, or has he still been out there Kirk-ing around the Galaxy trying to make his perfect baby? Did he age himself up to meet his son? Guess he could have, but what's the point?
*A human body, because, if I'm remembering the movie correctly, he explicitly wants to know what it would be like to be human. Not Kree, not an Eternal, not Shi'ar, etc. Human. Because reasons. Then apparently he goes all over the galaxy looking for space love before trying out Earth. Or maybe he's also got a lot of dead earth-kids in that big pile of bones?