CHECK OUT MY WORKAROUND:
It was the same here for me with three 21000 px files from the Nasa. But i was able to render them in half resolution, not full.
i need a 1920×1080 result:
In the render settings dialogue i changed the resolution to half size.
in the output module i resized it to 200%.
what hapens is, that a 960×540 version will be pushed to 1920×1080.
so there is a 50% quality loss, which ends in a blurry result.
so i avoid this reduction through setting my render comp to the double size of 1920×1080 to 3840×2160 as the first step of all.
Then, the 50% quality loss is there, but not visible 🙂