This is not a sequel to the 2005 movie, but actually a prequel to the 2014 Godzilla. They are setting up King Kong v Godzilla as the third in the Legendary Godzilla series.
2005 movie: events take place on skull island in 1933.
2017 movie: events take place on skull island in 1973.
It's a sequel, even if it doesn't reference any of the events of the previous movie.
>> They are setting up King Kong v Godzilla as the third in the Legendary Godzilla series. <<
In other words, ANOTHER remake.