“I feel like I’m in a fairy tale,” Sean Wang said to the sold-out crowd gathered at the Ray Theater in Park City, Utah, last month for his Sundance Film Festival debut.

Mr. Wang, a 29-year-old filmmaker, was dressed in a black suit and white Vans (a nod to his skateboarding roots). He grabbed his chest in a show of how fast his heart was beating as he introduced his film, “Didi.” It is a coming-of-age story about an angsty, insecure 13-year-old Taiwanese American boy trying to find his place in the world.

“I’m just going to take a few seconds to take this all in,” he said before snapping a photograph of the audience. The warm crowd included Mr. Wang’s family and friends, the film’s cast and crew, and a handful of potential buyers who have the power to transform his station in life from aspiring filmmaker to bona fide Hollywood director.

It has happened before. Luminaries like Steven Soderbergh, Quentin Tarantino, Damien Chazelle, Ava DuVernay and Lulu Wang all went from hopeful dreamers to actual filmmakers in part thanks to the Sundance Film Festival, which just concluded its 40th year.