You hit the nail on the head. The issue is not writers wanting to tell stories that get people thinking about ethics and politics; the issue is that the writers

You hit the nail on the head. The issue is not writers wanting to tell stories that get people thinking about ethics and politics; the issue is that the writers can't restrain themselves from turning the show into a preachy, obnoxious mess. Older Trek series weren't perfect in this regard (to your point, DS9 had a couple of episodes where the writers very clearly took a side and were preaching at the audience), but mostly they were skilled enough to use a light touch and let the audience draw their own conclusions. The same is unfortunately not true for the writers currently in charge of Star Trek (or a lot of shows for that matter).