If you really believe that the only thing “younger generations” do is post on social media, I suggest you spend more time around high schoolers (for example), particularly those with limited financial means.
Reminds me of a friend who, few years ago, was a teenager of limited financial means. He earned his first real $50 through a phone. His laptop broke, and he didn't have anyone to borrow one from in time, so he ssh'd into a remote machine from his phone and did the work (some data wrangling task) this way. Where there's a will, there's a way.
But still, that in no way suggests phones are good at text editing or productive work. They're capable enough, if you have lots of will and no other option.
https://hanselminutes.com/615/developing-on-not-for-a-nokia-...
It's awesome that those with limited funds can still get stuff done, and phones are great for consuming information, but I don't think there's much argument against the efficiency gain that hardware keyboards, mice and larger screens with multiple windows give when you get into things that require fine tuning and multi-tasking like drawing, coding and video editing.
(sorry I know posts like this don't make interesting reading, I just know how frustrating it can be when you put effort into writing something to avoid being misunderstood but still get taken the wrong way... so wanted to point out that at least for this reader the negative connotation was not there)
They do when they're trying to create something more complicated than a social media post.