I doubt they teach "launch angle" as an inflexible mantra, rather, it's a swing designed to avoid driving low pitches (as more pitchers throw 2 seamers and changeups) into the ground - wouldn't surprise me if they teach a flatter angle when swinging at pitches waist high and above.
I do think the new coaching may be responsible for the high rate of Ks for so many minor league hitters - but we need tor reserve judgment, just like teaching a pitcher to throw a changeup, the first year or so it may be a disaster - until the player gets comfortable. And some of the high K rates may simply reflect past scouting philosophy, focusing on power rather than contact and plate discipline. Not sure anyone can save Ortiz.
Nor do I see any major negative trends with talent:
2016 draft: Moniak, Gowdy (year after TJ), Romero (4), Irvin (5), Dyer (8), J Garcia (10), Stephan (11), Hall (14)
2017: Haseley (1), Howard (2), Seabold (3), Lindow (5), Maton (7), Brodgon (10), Parkinson (12), Dohy (16), Listi (17), Jones (18), Russ (19), Hernandez (21), B Brown (33), Stewart (39)
2018: Bohm (1), Eastman (4), Vierling (5), Simmonds (6), Cotto (7), Pipkin (9), McKay (16), Killgore (17), O'Hoppe (23), Carr (31),
Harder to get a feel for 2018, but doesn't look as strong as 2017, which could be one of the best of the last two decades.
LA last four seasons:
Aparicio, L Garcia, Torres, Muzzioti, Morales, the rest are in GCL and DSL, so hard to judge.
Gogoliski and some Australia/New Zealand guys who are also too low to judge yet.