The Ki-Adi-Mundi complaints aren't so much about his age. Rather, that the character clearly states in The Phantom Menace that the Sith haven't been seen in a millennium. Thus, including Sith characters in The Acolyte means that he was either lying or unaware of the situation. Both are equally bad options and create a problem with the narrative. It's okay to admit the writers for The Acolyte didn't think that one through.
Well, if that’s the plot of The Acolyte, count me in! Lol
The Ki-Adi-Mundi complaints aren't so much about his age. Rather, that the character clearly states in The Phantom Menace that the Sith haven't been seen in a millennium. Thus, including Sith characters in The Acolyte means that he was either lying or unaware of the situation. Both are equally bad options and create a problem with the narrative. It's okay to admit the writers for The Acolyte didn't think that one through.
Did you watch the entirety of the show? It's only Vernestra (and maybe, Yoda) in the Order that at that point knows about the Sith. The rest are dead.