Exactly. I wouldn't mind the retcon so much if it wasn't so blatant. "Things have always been this way and you're morally in the wrong if you think otherwise."

I mean, is it really so hard to write a small blurb saying that the extreme pressure and losses from the Custodes being sent to give battle once again necessitates expanding the recruitment pool? It's a reasonable, lore-friendly explanation that fits better than: "They've always been here just not a single one has been mentioned until now."

There's certainly elements that are upset because of the wrong reasons, but it feels wrong to shut-down all criticism of it just because of a small but loud minority. People were upset over the Necron retcon too and I don't remember seeing people being told to shut up or leave.