I totally agree. What I'm genuinely just curious about, though, is why this will struggle to match IM3. I think we've all established that the movie has done terrific business in general. It doesn't change the fact that it has veered off course compared to another older and less well received film that doesn't have the same scope as CW (IM3).
I've been thinking about this since yesterday and it makes me see this in a new light: Instead of talking about how Civil War's box office has deflated, I think we should be talking about how IM3's box office was inflated. (I know some people have already mentioned this. I'm just expanding on it)
Looking at it that way, suddenly it all fits better. Both Avengers films stand alone as $1.4 + billion films, then you have an inflated Iron Man 3 at $1.2 billion due to massive hype and appeal after the phenomenon that was The Avengers, then you have the rest of the solo films, the biggest of which being Captain America: Civil War. The rest range anywhere from $200M + (The Incredible Hulk) to $700M + (Guardians of the Galaxy, Captain America: The Winter Soldier).
In a nutshell, IM3 is the outlier here and CW is performing like it's supposed to: an above average solo film, due to its scope, that's a tier below the big tent pole Avengers films. Otherwise, there is absolutely no reason why CW should be struggling to match IM3. No objective reason. I'm still waiting for some people to provide me with those, rather than blurt out how the movie is doing fine for the millionth time.