Was The Spy Who Loved Me (1975) a sequel to Goldfinger (1965) or was it another James Bond film? Considering if you never saw Sean Connery’s turn in Goldfinger, you would not exactly be confused about the plot of the Roger Moore outing.
A new Beetlejuice film is going to be its own entity. Just as all you need to know about James Bond is he is a spy for Her Majesty’s Secret Service, all you need to know about Beetlejuice is he is a funny, wise-cracking ghost.
There is a bit of an ulterior motive present here. The original film was made in 1988. A huge chuck of the potential audience never saw the debut of Beetlejuice. Creating a standalone film creates a fresh start. Do not be surprised to see the “2” portion of the film’s moniker dropped.