First of all let's define angst.
The word comes from existentialist Kierkegaard, used to describe an emotional state including unhappiness, anxiety and depression. Today, this concept is dubbed teen angst, indicating the emotional turmoil teens tend to experience as a result of changing brain chemistry.
Angst is real and it's fine to have angsty characters in YA - it wouldn't be realistic without all that emotional turbulence - but angst as a plot device, as a substitute for drama, isn't going to go down well with YA readers, considering 55% of those readers are actually adults.
Here's an example of angst as plot device:
The teen girl MC is in love with the dreamy boy and their romance is in the infant stages. Our MC sees the boy after school with his arm around another girl. Our MC assumes the worst. She goes up to the boy, maybe even slaps his face, calls him a dirty lying cheater and storms off in tears before giving him a chance to explain that the girl is his sister/cousin and therefore not a threat. Our MC now ignores the boy's phone calls, refuses to talk to him, continues to think the worst and makes a string of bad decisions based on a non-existent issue, which the author calls plot.
This is not drama, this is not conflict. This is a silly girl creating problems when none exist and the story can quickly spiral into melodrama where melodrama is sensational dramatic conflict that fails to observe the laws of cause and effect and generally blows things out of proportion.
When I was 16, the slightest issues felt like the end of the world so melodrama can be the teenage norm. However, reading a book where the plot is driven by imagined circumstances constantly blown out of proportion will sooner have me flinging the book across the room than sympathising with the teen MC who has fallen victim to her underdeveloped parietal lobe.
So what do you think about angst in YA? Were/are you an angsty teen?