It honestly was a bit of a rushed conclusion (sorry for the pun). It basically existed to give the series a bit of closure, but leave it open at the same time if that makes any sense.
By the end of it they were out of immediate peril, and sailing onwards to discovery (thankfully not a crossover).
Every time there is a kindo-of-open end to some story I feel like either the authors are incapable of making a meaningful conclusion, or the marketing team wishes to make another cash grab a sequel even though chances are extra slim.
Sometimes it is because there's a grand plan that the authors want to flesh out, but this seems too rare