A lot of people I know felt that SS and Civil War were similar. I know that every Marvel fanboy here on the boards thought Civil War was an amazing movie, but it wasn't that great. I liked SS and GotG better for the same reason - it something different from the standard MCU fare.
Like I have said here all along, SS appeals to a different demographic and that is why it is doing well. Even my daughter's friends that have not seen the movie (their parents think it is too scary/adult oriented for their kids) are buying the merchandise because it is cool. SS has the right amount of rebellious and irreverent tone to appeal to the 12 - 30 demographic, which is what is driving the film. BvS was not well received and had too many issues to be a leggier film, and Civil War is aimed at the very young (4 - 11) and their parents (30+) like the other MCU and Disney formula movies are (which is a larger cohort of potential viewers).
I also think we are seeing Marvel formula fatigue. The fact that Civil War/Avengers 3 could not do better at the box office, with Spider-Man included, than a very bad AoU may be an indication of this. I hope that Infinity War can correct this as the last three Avengers related movies (AoU, Ant-Man and Civil War) have not been as strong as The Avengers or Winter Soldier - maybe that was the peak for Marvel?