To a degree, sure tickets sold can provide context. But if say...Star Wars came out now, I cannot see it doing the same at the BO. Other Star Wars movies have made over a billion, sure. But those were sequels to the existing IP. If Star Wars itself had come out now, I don't think it's effect is the same. Back then, only way to see it for years was in a theater and only whenever it was re-released. It wasn't until several years after it home media became a thing.. same for Gone With the Wind. There is no way it sells the tickets it did today. This is why I look at everything as in its own era and its own circumstance. ie, what it cost to make, how much it made, etc.
I would be very much willing to say if First Steps came out in 2016. Same movie, no changes, it probably adds about 100-200 mil to its BO take. But that also ultimately doesn't matter. The result is the result. We will see how Doomsday/Secret Wars change the game and what happens from here onward. That's going to be more telling than anything we are arguing here.