Is it possible to make a movie with todays smart phone?
Most movie-makers use the best tools for the job.  For some people that tool is an inexpensive camera they can afford to blow up (crash cam).  For some it's light enough they can fly it on a drone.  For some, it has a large sensor so they can get shallow depth of field.  For some, it means being able to synchronize with other cameras so that edits are aligned to whole frames.  For some it means being able to use a specific lens that provides a specific look, or flare, or angle of view, or zoom ratio.

Merely capturing 2K or 4K resolution doesn't begin to describe the requirements for making a film.  The script, the actors, the wardrobe and makeup, the set design, the props, the lighting, the color scheme, the use of contrast, color, transitions, music, sound design, etc., are all as important, if not more important, than the camera.  When the time comes to bring all these elements together and make an actual movie, it becomes readily apparent what sort of camera, camera operator, and camera department will do the movie justice.