[ so he's curious now, is he? why wouldn't he be when ascension to celestia essentially means becoming a god? if only that were so simple, however. as if the gods of teyvat will make it easy for anyone to join their ranks. ]

Simply because you're given the capability doesn't mean you're assured, doesn't it? At the end of the day, the gods will be the ones to decide if a Vision-holder will ascend or not.

[ otherwise celestia would be crowded, and that won't do. ]

Why do you think the gift they gave you is called a Vision? Don't you find it a little strange to call an item that grants you the power to control the elements something related to the sense of sight?