This is an excellent article that outlines all the details but Conan O'Brien's insights summarize it,

But it was [Conan's] appearance on the YouTube talk show Hot Ones that really opened his eyes to the reality of late night’s decline. “That was the moment the scales fell from my eyes,” O’Brien told THR earlier this year. “If a guy can do World Series numbers with overhead that looked, to me, to be about $600, and you have every big star lining up to do his show or Chicken Shop Date … that’s when I profoundly understood that late night shows are in trouble.”

But it's not just late night, people just don't watch traditional TV. Sports and reality TV, but that's about it.

Yeah. They’re kinda “talk influencers before talk influencers,” and their shows would be uncompetitive on social media platforms. The only thing keeping them alive is attention inertia.

attention inertia.

Good label.

John Oliver does OK, but he's kind of journaltainment

That's fine, they're all terrible

Makes sense. I can't recall the last time I watched a late night show while it aired on TV. My youngest siblings (mid twenties to early thirties) have never even owned a TV. Any late night shows I would see are in clip form on YouTube or other internet platform. Short form, please, give me the good bits with ads I can block.

"journaltainment" sounds exactly correct.

Theoretically, late night TV should be fire. A team of writers creating topical commentary for an entertainer at the top of their game to deliver with relaxed content guidelines for that time of night. Unfortunately capitalism. Standards declined and advertising increased as the networks try to wring every last bit of profit out of the format.

I'll miss it, but mostly I'll miss the time in my life when it was enjoyable. News moved a little more slowly, experience hadn't stolen all the wonder of the world from me, and... I could stay up late and not be dead in the morning.

Theoretically, late night TV should be fire.

Technically it is. Kimmel's YouTube segments get millions of views. Colbert's YouTube segments got millions of views. Seth Meyers YouTube segments get millions of views.

And the quality is fire. As Colbert said in his recent Emmy acceptance speech, hire my (former) staff, they'll make your show better.

One of the issues is that the interview portion is cheap to produce. The news portion, by comparison, is expensive.

Who is still watching television at all?