Seems like some of the initial changes are reflecting more than just the evolving language. He’s comparing someone using informal slang “not gonna lie” against someone writing extremely formally “Hunger, that great leveller, makes philosophers of us all, and renders even the meanest dish agreeable.” which I’m not sure makes sense.
I think you can make it make sense if you think of it as "writing in a speech popular at the time". Nowadays we (sometimes, often?) write the slang we speak; in the 1800s, people wrote (and perhaps spoke?) in more flowery sentences. Romance novels might seem written in stilted language to us now, but in their day they were kind of like writing in slang is now.
Is that true though? I don't think the median population member spoke in this way in the 1800s. Obviously in 2026 we have a massive written record of the popular speech patterns of the entire spectrum of society, but that's down to the internet more than anything.