Umm yeah everything have been suggested that Orochimaru changed since 4th ninja war and now he's just another kurotsuchi from bleach doing these experiment as his only hobby instead of pursuing his goal which is why he's working for konoha or else why would Yamato would be watch over??
They're not brainless as you think they are.
What has Orochimaru done for Konoha exactly?
He's still pursuing human experimentation, and he's still obsessed with immortality. I wonder how well Konoha watches him when he can obtain and keep secret a stash of Sharingans for his experiments.
Also, if Orochimaru were serving Konoha, why would the Hokage need to sneak into his lair? He's not working for anyone but himself, as always.
Madara recognized his actions were wrong, Danzō was never a villain, and Kimimaro was more of a victim than anything else.