I think this is a major point as well. They took an incredible amount of care and patience in crafting their CU. Something like Civil War could have been a horrible mess, introducing Crossbones, Zemo, Black Panther, a new Spider-man. Also the fact that Vision, Scarlet Witch, Falcon, WS, and Ant Man are relatively new characters.
However they've had multiple movies to develop the relationships between Cap, Tony, Black Widow, and Hawkeye, so there was plenty of familiarity for people that have seen most of the movies.
On the other hand this was the first appearance of a new Batman, Luthor, and Wonder Woman, and only the second appearance of Superman after a solo film with mixed reviews. They just put too much weight on one movie, and as a consequence it feels rushed and at times incoherent even though it has a long runtime. I wish they would have had the patience to build this slowly, getting Batman and Superman onscreen together for the first time is an amazing opportunity that ennds up feeling somewhat wasted.