Why did I like Arrival II? Mainly because I liked THE Arrival ((not to be confused with the pedantic (boring) Arrival (no "the")).
The connection was made clearly, yet unobtrusively. The main characters faced the same dilemma: aliens (extraterrestrials, no political connections) on a mission to conquer earth for personal use to the detriment of residents (well, maybe a little).
I thought the flashbacks were very well timed and smoothly carried over from the original entertainment ratio into this production. That created clever ironic situations, while maintaining independent plot twists. Overall, a sense of brooding loners fighting to save the planet against all odds lost none of its luster, passion, or cogent messaging. Arrival II also maintained the sense of humor and suspense in The Arrival.