– During one of the very last episodes of “Modern Family,” closet king Jay Pritchett spent part of his Paris vacation visiting a burnt-out Notre Dame.

“It used to be so impressive back in the day,” he said, gazing wistfully at the cathedral from a distance. “It’s just a shell of a former self. Its best days are behind it.”

Cynics might say the same thing about his sitcom when the final episode airs Wednesday.

At its peak, ABC’s longest-running comedy series drew nearly 13 million viewers; these days, it’s lucky to bring in half that number. It won the Emmy for outstanding comedy series for its first five seasons, a streak matched only by “Frasier.” It hasn’t even received a nomination the past two years.

But “Modern” hasn’t really changed much since it debuted in 2009. We have.

While developing a show about a multigenerational clan in suburban Los Angeles, co-creator Steven Levitan warned creative partner Christopher Lloyd that opening the series with gay couple Cameron Tucker and Mitchell Pritchett adopting a baby might be the kiss of death.

“As soon as we landed on that and locked it in, I remember saying to Chris, ‘Well, there goes Middle America,’ ” Levitan said in January at the TV Critics Association press tour.

But the executive producer’s fears were put to rest two weeks after the pilot aired when a crew member shared details from an encounter on another set.

“This Teamster guy, who looked really scary, came up to him and said, ‘You work on that ‘Modern Family?’ ” remembered Levitan, whose previous credits include “Just Shoot Me!” and “Wings.” “The guy was a little bit taken aback because he’s like, ‘Oh, no. Here it comes.’ And then the Teamster just looked at him and said, ‘I like that Mitch and Cam.’ That was the reaction we got. We got zero blowback. They were embraced because, here was this couple whose first priority was their baby and raising it right. And people just said, ‘Well, it’s hard to argue with that.’ ”

Still, the actors knew they were participating in a groundbreaking idea in TV history. “Will & Grace” had premiered more than a decade earlier, but that sitcom’s gay characters never kept a romantic relationship for very long.

“I think it was revolutionary back then, and I don’t think it’s as revolutionary now,” said Jesse Tyler Ferguson, who played Mitchell. “I think that’s a great thing.”

“Modern” was also ahead of the curve in casting.

In addition to having Mitch and Cam adopt an Asian-born baby, the show had Jay Pritchett in a May-December marriage to Colombian native Gloria, whose mastery of the English language was a lot less impressive than her fashion sense.

By 2011, Sofia Vergara, who plays Gloria, was the highest-paid actress on TV, thanks in no small part to her numerous commercial endorsements. Forbes has placed her at the top of that list every year since, an unprecedented streak for an actor of color.

“I never thought I’d be able to get a job that was so successful sounding like this,” Vergara said. “I might not ever get a job again, but now I have the money. I can sit in my house.”

Been there, seen that

In many ways, “Modern” was nothing new.

The mockumentary format already had been mastered by “The Office” and “Parks and Recreation.” The physical humor was straight out of the Lucille Ball school of clowning. The constant misunderstandings, laced with sexual innuendos, could have been lifted from yellowing “Three’s Company” scripts.

But the delivery was so sharp that the main cast — which would rack up a total of 29 Emmy nominations and six wins — could trick the audience into thinking they were seeing it all for the first time.

“There’s the cliché that you don’t realize what you have until it’s gone, but that is absolutely not the case here,” Levitan said. “I can’t tell you how many times we’d be shooting and we would stop and say to each other, ‘How lucky are we?’ There was never a moment anybody on this cast was, like, ‘I’m going to leave for better things.’ Nobody ever thought about it for a second.”

The fact the core cast stayed with the show its entire run meant that younger members of the cast got a graduate degree in acting, thanks to veterans like Ed O’Neill, who had previously spent 11 seasons on “Married ... With Children.”

“I was 10 years old when I started, so I really didn’t have an idea of what was happening or some of the jokes would just fly right over my head,” said Rico Rodriguez, who played the super-sensitive Manny Delgado. “Ed made sure I understood things and helped me when I would get excited. I would mumble and he would help me with that, too, slow me down. If I had trouble, he was always there for me.”

For viewers, it was a kick to watch the TV kids grow up in front of their eyes. But it wasn’t always a ball for the actors.

“There was definitely one season for me where I hit puberty right as we went on break, and so I came back and had completely changed but not quite enough,” said Nolan Gould, who was 11 when he originated the role of slow-witted Luke Dunphy. “I couldn’t get through one sentence without my voice cracking constantly.”

It was worse for Ariel Winter, who was also 11 when she was cast as Luke’s brainy sister, Alex. As she got older, Winter was often a victim of body-shaming comments from online bullies. Her co-star Sarah Hyland calls them “keyboard trolls.”

“When you grow up on TV, millions of people think that they know you really well, and that they can comment on everything you wear, everything you do, or how you grow up and change,” Winter said. “You try to be nice about it and hope their day goes better. I’m sure I said a couple things I regret, but I never wanted to hurt anybody. Honestly, for me everything is a learning experience.”

Despite the hardships, Winter and her castmates realize that “Modern” was a very special series. It may take a while for viewers to realize the same. Sometimes you really don’t know what you’ve got until it’s gone.

“I think everybody is going to go on to do all kinds of great stuff, but this show really does kind of ruin you,” said Ty Burrell, who played the unsinkable Phil Dunphy.

“The people, the quality of the material, the hours, frankly everything about it. It’s going to make it hard to follow this job.”