Greg Berlanti’s adaptation of Becky Albertalli’s 2015 novel “Simon vs. the Homo Sapiens Agenda” is being advertised as the first Hollywood romantic comedy about a gay teen, and in that formulation the “Hollywood” part I especially significant. In an effort to appeal to as many moviegoers as possible, any hint of edginess in the story has been smoothed out; what results is a good-hearted but exceptionally bland “coming-out-of-age” movie modeled after the John Hughes high school pictures of the eighties. Though set in the present, it seems to reflect a cinematic mindset of the distant past. It also doesn’t help that it’s just not very funny.

Simon Spier (Nick Robinson) is a good-looking high school senior with loving parents (Jennifer Garner and Josh Duhamel) and a younger sister (Talitha Bateman) he actually gets along with. He has a clique of close friends—his BFF since childhood Leah (Katherine Langford), feisty campus newcomer Abby (Alexandra Shipp) and jock Nick (Jorge Lendeborg, Jr.). Simon tells us in voiceover that he’s “just like you,” except that he has one huge secret—he’s gay, something evident in his close but anxious observation of the stud yard guy who works across the street.

The only fellow who’s already come out on campus is Ethan (Clark Moore), whose ostentatious put-downs of the school’s resident dumb bigots Aaron and Spencer (Tyler Chase and Terayle Hill) are hardly Simon’s style. Yet he’s uncomfortable with his forced closeted status, and when an anonymous writer, using the name Blue, announces to the school that he is gay, Simon writes back using an alias too, saying Blue is not alone. The two begin exchanging messages.

But who could Blue be? Simon becomes obsessed with finding out, and imagines—in fantasy scenes—that it might be the nice black kid Bram (Keiynan Lonsdale), or Cal (Miles Heizer), the morose piano accompanist in the drama club, or Lyle (Joey Pollari), the waiter at the diner where the kids hang out. He’ll investigate each of them, but in talking with Blue in increasingly intimate messages, Simon makes a dumb mistake: not only does he use a library computer, but he fails to log off, allowing Miles (Logan Miller) to call up Simon’s e-mail exchanges.

Miles is a desperately needy guy who wants to link up with Abby, and blackmails Simon into helping him. In doing so Simon betrays not only her but Nick, who confesses he likes her too, but Simon advises him to romance Leah instead. The convolutions increase until Miles makes a spectacularly public approach to Abby and, when he’s rejected, outs Simon in a pique. Simon is soon ostracized by his friends, ridiculed at school, and uncomfortable at home, where dad has always jocularly remarked on Simon’s manliness and now understands how painful those comments must have been.

Fear not: all will end happily as Blue’s identity is revealed and he and Simon will finally come face-to-face, ending the stream of gay red herrings the movie has been strewing about. (The final unmasking, however, requires an explanation of a past sequence that, frankly, doesn’t convince.) His friends will also rally around Simon again, his family will show its utter support, and drama teacher Ms. Albright (Natasha Rothwell) will come down on dopey Spencer and Aaron like a ton of bricks. Even Miles will get a chance to redeem himself.

But that’s really not enough, audience-wise. Miles is such an obnoxious twit from beginning to end that he’s not amusing, the way Hughes’s troublemakers were, but simply grating. And the film is saddled with another major irritant in the character of Vice-Principal Worth, a goofily anxious-to-be-chummy guy whom Tony Hale plays in what might be called full Jerry Lewis mode and is given way too much screen time.

On the other hand, Robinson (from “The Kings of Summer,” among other films) is a pleasant presence, and Langford, Lendeborg and Shipp are likable as well. Most of the other young actors are agreeable too, and Rothwell contributes a finely-tuned portrait of comic frazzle as a teacher who has little tolerance for ineptitude or stupidity among students. Duhamel and Garner are both okay, but no more.

On the technical side the picture is fine, with John Gleserian’s widescreen cinematography, Harry Jierjian’s editing and Rob Simonsen’s score all unexceptionable.

But coming so soon after “Call Be By Your Name” and other superior independent films on similar themes, “Love, Simon” seems more pallid throwback than progress, so anxious not to offend that it settles into a sitcomish rut. Nevertheless it will be interesting to see whether Berlanti’s benign caution will attract the mainstream audiences the studio is obviously trying to corral.