I may be wrong but I don't think there are any "cutscenes" missing from it - there's a lot of
story missing, but that's because a lot of the story isn't told in cutscenes.
Any conversation that just takes place with textboxes and emotes in 'normal gameplay' mode, with your UI and other players visible, isn't a cutscene even if it's important story progression.
It's only when you cut to a more cinematic presentation (leaving your character idling with a 'filmstrip' icon to any other players) that it counts as a cutscene.
Also any scenes that take place within dungeons (eg. if you were trying to go back and watch scenes from the ARR finale dungeons, back when new players were often forced to skip them to keep up) aren't included in chronological order in the MSQ section, but in a separate 'dungeons' tab - so some people overlooked that and didn't know where to access them.
For revisiting non-cutscene dialogue I've been using the
Garland Tools website, which has a text record of all quest dialogue except voiced cutscenes.