Old school network CBS ordered an old school Supergirl pilot episode and that is precisely what producers Greg Berlanti & Andrew Kreisberg of the CW Network's Arrow and The Flash, plus "new girl" Ali Adler (Glee, Chuck) delivered to them. Clearly some sort of checklist was involved.
Unfortunately all of the DNA fragments used to create this version of DC Comics' Supergirl don't quite fit together. The origin story is not belabored, but is hindered by obvious contractually-mandated limitations on the use of the necessary but unavailable Superman. Too much show "mythology" is shoehorned into this 45-minute pilot episode to allow viewers time to warm up to any of the characters that have been introduced.
After four seasons, Arrow still includes its weakest element (flashbacks to an Oliver that we know will survive every season-long threat he faces.) Those flashbacks kill the momentum of the current timeline stories. Every. Single. Episode.
The Flash began with guest appearances on the established Arrow series. Early episodes of The Flash had many awkward moments, but the show came together and eventually began to tell some extremely entertaining stories.
Bad indicators for Supergirl include unflattering mom glasses, non-ginger non-freckled Jimmy Olsen, Kara & Cat scenes that drag on way too long, dull action and effects that fizzle.
The pilot is a yawn, but the producers involved know how to make this sort of show work. So keep watching for a few more episodes. It could go either way.