Good science fiction shouldn’t be a sobfest. That’s the No. 1 issue facing “The Adam Project,” an artificially emotional Ryan Reynolds vehicle on Netflix about a time traveler who meets his kid self. The film is drowning in sap.

You yawn through the uninspired action sequences — just 30 years from now, we apparently will wield cheap-looking lightsaber rip-offs — and then are nauseated by overdramatic exchanges such as this:

Character 1: “But what about your future?”

Character 2: “YOU’RE MY FUTURE!”

Subtle, guys.

The tip-off that “The Adam Project,” which at one point was set to star Tom Cruise, would end up as suburban tweedom with spaceships is the casting of wholesome Jennifer Garner as the mom of 12-year-old Adam (Walker Scobell).  

He’s been bullied at school since his physics professor dad died, and his mom is beginning to date again. One night when Adam is home alone, a stranger shows up in the backyard shed, and we quickly learn that the intruder is Big Adam (Reynolds) from three decades down the line.

Letting us know Big Adam’s identity from the outset is a huge mistake because it gives the pair nowhere to go. It’s like if Darth Vader dropped “I am your father” in the first scene of “Star Wars.” From there, the movie isn’t much more than Reynolds doing his usual spastic shtick while a preteen mimics him.

Big Adam’s goal was to hop back to 2018 to destroy time travel and prevent the death of his wife (Zoe Saldana) at the hands of Maya, an anodyne villain played by Catherine Keener. But he overshoots and lands in 2022. (Terrible choice, man.) Big Adam’s dad (Mark Ruffalo), it turns out, is the guy who invented the technology. Together, the Adams venture four years into the past.

Whom this movie is for, I couldn’t tell ya. It’s safe and condescending enough for little ones. For instance, when guns are used in a fight to kill super soldiers, the baddies poof into a fume of pink dust. Death has never looked so cute! Although it is a soft PG-13, “The Adam Project” is stylistically geared toward 5-year-olds who aren’t going to watch a movie about time travel and frayed parent-child relationships. 

Today’s teens and 20-somethings are too smart for a movie so dumb.

Were the material better, it would be perfect for its director, Shawn Levy, who helmed the tremendous “Free Guy” and produces another youthful sci-fi adventure on Netflix, “Stranger Things.” But “The Adam Project” is a return to his less illustrious days of schlock and awww: “Night at the Museum 2” and “The Internship.”

To partly quote Dr. Emmett Brown, Levy needs to go back … to the drawing board!