It is criticised in-universe by characters we are clearly supposed to agree with, and in an arc that demonstrates StarClan's capacity to make poor decisions. I mean we as a community knew StarClan was on some shit but TBC showed that the writing team agreed. Yes, it is sad that the Dark Forest cats who helped the Lights in the Mist will never have a second chance, but that's not a bias on the part of the authors, but on the part of StarClan.
Just seems strange to assume we're not supposed to critique StarClan and that StarClan being anti-redemption means the books are anti-redemption.
on another note about Warrior Cats and morality, and common misconceptions, Tigerstar wasn't "born evil". He was born with great potential, and the potential for good was squandered early in life with an absent kittypet father and an abusive mentor. Yes, StarClan suggests killing Tigerkit in fear of what he could become, but Doestar is clear when she tells Pinestar that, with guidance, Tigerkit could become a great and noble leader. That just isn't what happened.
Anyways rant over I just dislike when readers take the least charitable interpretation of every single thing that happens in these books.
I think most of StarClan assumed Tigerkit would turn out evil because they didn't trust Pinestar not to turn kittypet, based on ~facts and logic~. Doestar, having been the one responsible for Pinestar's leadership in the first place, continues to believe in him in spite of the most likely future StarClan sees. She wants to make that unlikely future where Pinestar raises a "good" Tigerstar happen.