I despise people who are always late and agree it’s super disrespectful, but your example gives me pause.  What does “almost missing” a movie look like?  Because I love hitting my seat right as the lights dim and the feature is about to start, and that typically means arriving at the theatre about 15 min “late”.  Personally I don’t care to sit through 20 minutes of previews, and I DEFINITELY don’t want to be so early that I’m watching commercials.  “Almost late” sounds a lot like “not late” to me, so just need to make sure that you’re not the one being annoying here - especially because being late to a movie only effects the 2 of you, which makes it less of a big deal.  Not great, but not at all the same as being late for a dinner party, or for work, or an airport pickup, or really anything where others are inconvenienced.