Nagato doesn't have an answer to Tsukiyomi just as Itachi doesn't have an answer to shinra tensei. Saying that is pointless and people are just directing the fight the way they want to. In the manga, Itachi sealed away Nagato and figured out his weakness for chibaku tensei. If he wanted to, as an Edo w/ unlimited chakra, he could have just spammed Yasaka Magatama two more times and saved the chitchat w/ Naruto and Bee, but he decided not to, because those two characters were there. That just proved that Edo Itachi>Edo Nagato. Also mainly because, if you kill an Edo they just keep on coming back until you seal them, and Nagato has no sealing methods for Edos.
When they were alive, they were both nerfed, Nagato even worse than Itachi. They have always been equal because of that. They will always be considered equal, it's what Kishi wanted to portray and it's going to stay like that considering that they're both dead and neither are getting powerups soon.
But if Nagato isn't crippled and is actually healthy, then he demolishes Itachi.