(after edit)
I have no issue with the text size, I have an issue with enormous empty space around the text. It's fine if it's not perfect on a 21:9 display, but this wouldn't look good even on a 16:9 display.
I'm also fine with the text not taking up the entire width, I aggre that it's less readable. But I think the window (not the text, the window) could utilise the width better.
I say that the messages could be a little more spread out (i.e. my massages could be a little to the right while other's a little to the left) and just like the left sidepanel appears and disappears when the window is too thin, more sidebars could appear to the right when the window is very wide.
Gnome does have a lot of strong points, I personally use both