Too many things are going on in this movie. From the squadron's action, the situation in Area 51, Levinson's dad, the romance and subplots. And the movie tries to portray them squarely - although eventually they connect to each other, it makes all the sequences give no importance to the audience other than showing, "hey, this is what this character is doing during this doomsday."
This is a very bad move, as portraying every characters give not enough space to explore more of their persona. It left no room for the audience to relate/empathize with them, and as a disaster flick, this is such a waste because it really makes the human drama feels lackluster. The impending doom is all but menacing: yes, we get to see the world being destroyed by the immensely powerful alien technology, but we don't get to see the terror it gives to the people in the movie. People are screaming, but none are terrified. Not to mention the constant jokes pulled by comic relief characters really take out the seriousness of the damage.
The plot is also predictable and the movie doesn't seem to be shy from showing it blatantly from the start. Especially if you've watched the prequel, you'd know exactly how things will end. The action and dogfight sequence too are also so-so.
Besides the stunning CGIs, there isn't much to be seen from this movie.