Then, according to your personal, subjective definition of the phenomenon, the Tribunal and the Empire of Uriel VII are also evil. So are the rebels in this story. All Daedra are evil and so are all Aedra, and by thus so would be the Imperial Cult.
Hence, there are still shades of grey. The Empire, many of the Aedra, the rebels, and Tribunal still respect the lives of their subjects far more than the new "champion", as evidenced by many of their acts.
Though Vehk, Almalexia, and Sotha Sil killed Nerevar in an act of evil, they took the power of the heart to protect the Dunmeri people. Almalexia turned indisputably evil in Tribunal when she put her power and the unity of the temple over the welfare of the people. Vivec accepted the fall of the tribunal, and aided the Nerevarine against Daggoth, despite knowing it would bring down the Tribunal. While the suppression of the Outlanders could be considered evil, most of their policies were benevolent.
I am not entirely sure about all the Aedra, but Stendarr is known to be good because he is about saving lives and protecting the weak against oppressors. Also, the Imperial Cult aids those in need, healing those who come to them, curing the blighted and diseased, and offer shelter and sanctuary to those in need. They also unite communities, and give people reasons to live.
The Empire is very neutral in its rule. It generally suppresses needless wars between the provinces, and offers as many legal protections as it can to the people. However, it sees itself as neccessary to the survival of Tamriel, and offsets its general benevolence with suppression of rights and life in the provinces, as it tries to balance the unity of the empire with the rights of the governed. Remember, Tamriel has earned its nickname as "the Arena", and so was arguably the lesser of two evils. I am not entirely sure how the Amulet of Kings came to be, but without it, the Empire also protected Nirn from a completely disasterous Daedric invasion, from a prince who claims to be merely the embodiment of Destruction, but gleefully infringes on Molag Bal's, Namira's, Mephala's, and Boethiah's territory.
The rebels in this RP are not evil because they are fighting for the right to life and liberty of all subjects, against a force that does not care about the welfare of the overwhelming majority of the population. Though they may engage in atrocities and cause tragic civilian deaths, they understand that the cost the "Champion" wants to impress on society is not worth what benefits the Empire used to offer to the provinces. They see the Empire as completely off-track, conquoring for the sake of conquest, unity for the sake of power of the head of state. The benevolence has been removed, and only the oppression remains.