Most Fate writing in a nutshell (interestingly FGO actually has more consistency):
“Well I wanted to do certain things because they look cool. But then I realized they broke the rules I myself established in the script…But then I was like, ‘I don’t care’.”
When writing science fiction and fantasy should be more like:
“No I’m sorry that’s a violation of your frame of reference.”
The “gods” in Fate aren’t gods, they are aliens who were worshipped as gods by humans who didn’t know any better. So the claims about what the gods are capable of are based on the false beliefs that the humans assigned to the aliens even though those are properties that the aliens couldn’t possibly possess. For example no alien can destroy the universe or even a planet, that is a power beyond the capabilities of the aliens since the aliens are ultimately finite beings the same as the humans and cannot even destroy a planet let alone every planet everywhere. If they could have destroyed a planet then the Earth would have already been destroyed. The fact that the Earth is still around is proof that the aliens cannot destroy planets. But the humans who worshipped the aliens as gods didn’t know this. They didn’t even know what a planet was. So to those early humans their nation might have been what they considered to be the entire universe because they had no knowledge of what planets and stars were or even the true size of the Earth compared to that of their village or the Earth compared to the sun.
This creates an interesting bit of worldbuilding.
The divine servants that get summoned aren’t based on the real aliens who were worshipped as gods but on the conceptual beings that the humans who worshipped the aliens thought they were worshipping. Hence why most divine spirits need a real body to act as a medium to anchor the conceptual being that never existed in reality. The Ishtar in Babylonia doesn’t know where Gugalianna is because the Ishtar in Babylonia is based on the conceptual being that the Babylonians worshipped and so lacks the knowledge of the real Ishtar who left Earth but is still alive.
This is necessarily true given the events in the first singularity where Avenger Jeanne is created based on the British concept of Jeanne who the British considered to be an apostate witch. Avenger Jeanne has no knowledge of Jeanne’s life outside of her being tortured, humiliated and then burned to death by the English because that is the limit of the English knowledge of Jeanne. So when Ruler Jeanne asks Avenger Jeanne if Avenger Jeanne remembers her childhood and Avenger Jeanne does not this is what we the audience are meant to understand. Neither Jeanne is the real Jeanne, rather both are based on humanity’s concept of Jeanne. One concept is Jeanne the saint and the other is Jeanne the witch. All servants are therefore based on the concept of the being and are not the real being.
if you want to take this concept even further then we can even conclude that the servants Goduka/Ritsuka summons are conceptualized versions of the servants she/he encounters, a servant based on a servant. This is why Goduka/Ritsuka can summon servants she/he meets as pseudo servants. Since a pseudo servant is a normal human with a servant grafted into them then a pseudo servant is not summonable since the only part that is summonable would be the naked servant without the vessel. You can’t summon Rin Ishtar, you can only summon Ishtar and then place Ishtar into a new human host. But Goduka/Ritsuka DOES summon Rin Ishtar which can only mean that the thing summoned isn’t the pseudo servant she/he met in Babylonia but a new conceptual being based on Goduka/Ritsuka’s own concept of Rin Ishtar.