First season was great, but it really squandered the potential that got it saved and moved to the CW. The pluses are Melissa Benoist, this really is the role she was born to play and is easily the best actor talent wise in the Arrowverse. Also, the cast has a great chemistry and brainiac has been a real plus and injected must needed comic relief. The central role Kara and Alex has as sisters is also novel and this show does not fall back on the sometimes awful romantic subplots that plague the other DC CW shows.
But the bad is the writing. It is just awful. Supergirl is one of those shows that is too adult for kids (lots of politics and sexuality issues that parents would not like) but too sloppy plot wise for adults. If it were a kids show, you could forgive it. But since it wants to be an adult show, just too many people notice all the holes, bad dialog and just poor world building.
This is a show where one character wants a baby..then doesn’t. One character makes a big speech about the president wanting to build a wall..yet on this earth an alien is secretly president and is (was) very pro alien, so what they heck was she even talking about?, major villain wants supergirl to reveal her “secret identity”, yet supergirl does not wear a mask and there is no reason why anyone would even think she has a secret identity..Just a very weird lack of attention to detail plagues this show, like it does not even care about what was established factually before on the show. It is whatever is needed for the plot of the week, even if it makes no sense to people who watch it all the time
The politics are just high school-ish and eye rolling even if you agree with the overalll points. The writers are just not talented enough..This season, the pro immigration point does not even make sense in this universe..since it has been invaded by aliens like four times who tried to kill everyone on earth and the president was a secret alien pushing an pro alien agenda. Common sense would tell you that if any world would be angry and fearful of aliens, it is this one..but Supergirl and her team basically just tell us that anyone who is anti alien is some dumb nazi and per se evil. It is nuts as the point they are trying to push just does not mesh with this universe. Good writers could probably make a great story about how people can be welcoming even when they have every reason not to be, or show supergirl reflecting if all the literal aliens on this earth has really been a good thing for the people..but this show does not have good writers and you have cognitive dissonance watching the good guys trash people who would seem to have very good reasons not to like aliens..because they don’t like trump? It is putting a square peg in a round hole.
This show had its chances..It should be better four seasons in. great lead actress cannot save terrible material. I gave it a thumbs up just for the characters and when it is goofy and fun. Just not enough of that.