Kancolle season two definitely does not feel like a season two. The anime has a way darker tone, actual people, more/less realistic naval battles, different characters and shipgirls that retire instead of sink. You shouldn't watch this with the expectation of getting cute shipgirls doing cute things at the very least. The story is acceptable overall and is mainly about naval battles. The tone is way darker than before and everything seems more depressed. Not everything that happens makes sense and there's a very confusing deus ex machina in the final episode. As far as the naval combat itself goes the anime abandons the ideathat fleets have to consist of 6 shipgirls which the first season probably inherited from the game. Shipgirls now also have Anti-Air and (generally) don't use their main guns to shoot at planes anymore. There are also depth charges now to deal with submarines. On the other hand abyssals can now merge together to form a single huge abyssal which seems like an odd quality for ships to have and completely unrealistic.

All of the important characters weren't actively featured in the previous anime. There's also actual humans now. The admiral is a person, there's naval workers on the docks and there's normal citizens living outside of the naval base. Shigure is the main character and she suffers from PTSD. There's some character development but it's limited by the large amount of characters and the decrease in episodes from 12 to 8.

The quality of the art depends on the episode you're in. The first episode has stunning art that completely blows the first season out of the water but over time the quality decreases a bit yet still remains above the level of the first season. There is CGI but it's better and there's less switching between CGI and animation making it less disturbing.

Overall the second season of kancolle is very different from the first and the movie. The tone is way darker and most things are different. It can be interesting to watch depending on what you're interested in as long as you're aware of the change in atmostphere.