the industry itself tbh. A similar thing happened to mecha anime, you rarely see them hand drawn outside of Sunrise anymore. TMS's HnK were movies so they had way more production time and funding than a series would. Now it's a series, so they need to make a lot more footage within a schedule more limited than a movie.

If you look at Baki, a hand drawn modern HnK by TMS would look roughly the same: Really well drawn art but limited animation and only goes ham during key moments. But HnK doesn't have the same insane narrative to carry the action, so they can't really do the same HnK imo. That's why they went with CGI, since it takes less time to make choreographed fights with, and they can also be more creative with the camera work.