In the Prime verse the Romulan War happened roughly 100 years earlier. On TOS there were still those who were bitter about Romulans. Those of you TOS fans, I am sure will remember Stiles in Balance of Terror
. He was clearly bitter, and I would dare say prejudice (Remember how he treated Spock when they showed the Romulans looked like them?)
Yet, the fact a Romulan blew up an entire Federation world, is just let go. I get that they are rebooting things. However, anything before 2230 is thought to be the same in both timelines, since that is where the two timelines split. So older fans are to assume because of this. The Federation is supposed to say, "Oh, it's alright that you blew up one of our founding member's homeworld, and killed 6 billion Vulcan and countless non-Vulcans."
To me it is kinda like Japan bombing Hawaii, and the US just saying, "it's alright, we are not going to do a damn thing about it." We didn't do that, instead we bombed Hiroshima and Nagasaki. I am not condoning it, just using it to make my point.
Rumor has it we might meet more Klingons in STXII, seems to me we need to deal with the Romulans. And yes, I get this is not the act of the Romulan government. But wouldn't that have been a better battle for Admiral Marcus to try to fight? He would have gotten a hell of a lot more backing for it.