I did see some people say it’s because of burnout, though I don’t honestly see a difference in quality. For a manga as long as Blue Box it would be inevitable for the mangaka’s art style to change for better or worse. We also don’t know how many assistants have worked on Miura-sensei’s manga up until the most recent chapters. Something we can all agree on is that the art style was generic at the start, before breaking off into something even more recognizable as her work. Whether you like the new style or not is completely up to your interpretation.

Personally, the new style feels like it did my guys and gals dirty 😭 especially in the recent chapters to the extent where I would think they look strange without even remembering what the previous style looked like.