they have the actors say “these events weren’t supposed to happen” repeatedly on screen?
The purpose of the “time has been altered and we need to fix the timeline” conversation that occurs near the beginning of every time travel story is definitely not to inform the audience that every subsequent installment of Star Trek will occur in an altered timeline.
In fact, it’s just the opposite. The entire reason the characters are so concerned with restoring the timeline is that they want to return to their lives in an unaltered timeline.