JRPGs are adventures

Its a mistake to treat them as RPGs, as they're more of Adventure-RPG hybrid: the terms "rigid plot", "film-like" experience are actually fairly normal in adventure games.

Adventures are story-centric experience with characters merely tools of the plot, not min-maxing superheroes who slay dragons by the bucketload.

JPRGs and Adventures are both linear and fairly rigid in design. The penchant for cinematics and film-like stuff is a legacy of past where such effect were impressive.