Are this the same people though?

Split screen is a social feature. Just look at Youtube playthroughs of partners playing Baldur's Gate 3 together in split-screen. It is a different thing to online play.

This.  Playing Tiny Tina split with the wife is awesome.

I am sure there are a small minority that use it, however, Online has replaced Split Screen. It's just a superior and more convenient way of playing MP games.

Arguing otherwise is like saying broad games are superior to video games because it doesn't rely on electricity. 

It's cool as a teen with limited budget but as an adult you should own enough TVs, computer monitors, notebooks and consoles to set up multiple gaming systems.

Why play splitscreen on one display when you can simply set up a temporary monitor next to your TV so everyone can have their own display?

Splitscreen is definitely the inferior choice here.

Nintendo is still a powerhouse in split screen, couch multiplayer goes without saying. They are not slow-moving away.

It's a shame that the same can be said about other developers that actually take away that feature from their games. Instead of reuniting people to play a single copy of their game, they want each of these individuals owning their own copy and playing online (paying subscription).

It's that simple, taking away options that are not beneficial for them and not because Split-screen is inferior. (Online is not perfect, you know) 

And I thought people here are pro choices, yet are defending the death of this option. Be certain that companies don't take away Split-screen only, but also couch multiplayer in general.

People tend to play online more and more instead of going to a friend's house to play. And I imagine developers and publishers know that it sells more: you need two copies to play online, but a single copy to play splitscreen.

You have a weird concept of superior. I didn't say superior, I said different. Your board game example is perfect. Neither board games nor vcideo games are superior, they are different for different use cases. Board games will not be pushed out because of video games, as they target a different experience. And I am for instance playing sometimes video games, sometimes board games and it is both fun, but different fun.

So online play also isn't superior, it is just different - as I said in my post ("It is a different thing to online play"). Online hasn't and can't replace split screen, as it is a completely different experience. That's why Baldur's Gate 3 supports both: online play and split screen, as Larian clearly know that they cannot replace each other.

Playing games in the same room with a good friend decimates playing with a random stranger across the globe.

So buy two TVs, two ps5 consoles and two copies of the same game???  No.

Personally, I would like it split screen was still exist. But the moment online gaming got serious, I figured split screen and couch coop stuff would start to vanish off