? And Loki ?
That's something that changed in 2010s timeline. You can perfectly impact other timelines. It won't affect your original one, that's what the Ancient One said, but while remaining in this timeline, you can perfectly fuck it up. 2010s and 2014s timeline ARE fucked up now, even though we'll never get to see the proportions (unless we have spin-offs).
What I meant is that even though it's not Cap's original timeline, it's HIGHLY unlikely he doesn't give a fuck about billions of people being slaughtered. Especially if he knows how to prevent everything from happening.