I’m not sure which trailer you watched as there are different versions out there, but it does seem like you may have missed out on some crucial parts. For example, the question isn’t necessarily “why did he do it” but “why did we not notice something was going on” because, as you mentioned yourself, “we don’t talk”. And the show isn’t just going to be about finding out the cause, either, which the trailers actually quite bluntly push in your face: one main character has breast cancer, another is a recovering alcoholic who, going by the trailer, might be having a relapse (thus the “wake-up call?”), and the third battles depression himself which, surprise surprise, his friends didn’t know about. This is where the conversation can start properly.
DJ Nash hasn’t so much fielded the question about romantisizing suicide, he has actually denied that his show was doing so. The premise is loosely based on his own experience of losing a friend to suicide so I would assume he’ll tackle it with some delicacy. They’re going to air a suicide prevention PSA after the pilot and their actors received press training on how to speak about the topic when asked in an interview (I can give you links to all of this if you’re interested.)
If the show turns out to be everything you fear it is: by all means, trash it. I’m just saying that it seems a bit early for articles like this that might turn people away from a show that is genuinely trying to open a conversation about topics not often talked about. (In my experience, the mental health stigma is very much alive, despite your perceived wider recognition. Let’s not forget that we all live in our own little social bubbles.)