Let’s be honest. “The Big Bang Theory” was never a so-called “critical darling.”

In fact, producer Chuck Lorre’s comedy about a group of nerdy scientists and their pals has had its legions of sneering haters. “Too broad,” they insist. Too “old-school” with its canned laughter and march-time gags.

Once described by a witty tweeter as “the Nickelback of sitcoms,” “The Big Bang Theory,” which airs its series finale on May 16, never pops up in those “100 Greatest Shows of All Time” lists. And this week bloggers and journalists surely will expend thousands (millions?) of more words on the finale of “Game of Thrones” than they will on Sheldon, Leonard and the rest of the bazinga bunch.

Still, there’s absolutely no denying that “Big Bang” made a big splash in prime time and will be missed by many when it signs off for good.

The shining example of a “critic-proof” show, the series that Lorre and Bill Prady created averaged nearly 17.7 million viewers over its incredible 12-year run and has ranked as TV’s most-watched comedy for seven of the past eight seasons. Thursday’s hour-long finale will be the show’s 279th episode — a record for a sitcom filmed in front of a studio audience. Yes, more than “Cheers.” More than “Friends.”

So how did this happen? Johnny Galecki, who plays Leonard on the show, isn’t quite sure.

“If there was an exact recipe for the kind of chemistry that is here on the stage and in the writer’s room, every show would last 280-something episodes,” he said. ” … It’s just a really good group of people who wanted to do a good job, and make a good show, and we have.”

Earlier this year, reporters were invited to observe a rehearsal run-through of a “Big Bang” episode on Stage 25 at the Warner Bros. Studio in Burbank. Afterward, in a brief ceremony attended by studio bigwigs, the stage was renamed in honor of the show, complete with a special plaque. There were a lot of smiles and a few tears. (Only four other Warner Bros. shows have been so honored).

In trying to explain the secret of “Big Bang”‘s massive appeal, Lorre leaned on the word “community.”

“(It’s about) people caring for each other in different ways — and maybe not being so good at it,” he said. “Affection underlies all these relationships (among the characters), even the adversarial ones.”

Lorre went on to add that the characters aren’t “blood relatives, but behave like a family — they eat together, work together, make each other miserable like a family can do. But they’re there for each other when times get difficult. That’s aspirational.”

Still sitting atop the Nielsen ratings, “The Big Bang Theory” certainly could have aired even longer — and CBS did want more. But Jim Parsons, who won four Emmys for his portrayal of the quirky oddball Sheldon, announced last year that he wanted to move on. It was then that all involved decided to call it a wrap.

Parsons, who didn’t hang around after the stage ceremony to chat with reporters, had earlier told Entertainment Weekly that ending the show “was “very, very sad,” but it also felt “like we’ve chewed all the meat off this bone.” Parsons will continue playing his “Big Bang” character in some form, providing voiceovers for the spin-off, “Young Sheldon.”

Meanwhile, other cast members weren’t exactly eager to let go. For example, Kaley Cuoco, who plays Penny, told journalists, “I would have done 20 more seasons.

“It’s a magical place, but life goes on,” she added. “It feels good to go out on top.”

Cuoco explained that “Big Bang” succeeded, in part, because it offered a group of relatable people who evolved over the years. By the end of the show’s run, three of the four male characters — Leonard, Sheldon and Howard (Simon Helberg) — who started out as socially stunted and basically scared of women, were married.

“They’re special,” Cuoco said. “They were the underdogs at the beginning, although now I think they’ve totally come out on top. They’ve become cool. I still think we made nerdy cool 12 years ago when it wasn’t.

“And I think a lot of people thought this was going to be a silly show with two nerds living next to the hot girl. But we’ve completely changed that, and outgrown that. We became real amazing characters who have left a mark on people’s hearts.”

Contact Chuck Barney at cbarney@bayareanewsgroup.com. Follow him at Twitter.com/chuckbarney and Facebook.com/bayareanewsgroup.chuckbarney.

‘THE BIG BANG THEORY’

Series finale: 8 p.m. May 16; CBS

Retrospective special: “The Big Bang Theory: Unraveling the Mystery,” hosted by Kaley Cuoco and Johnny Galecki; 9:30 p.m. May 16; CBS