That said...I must confess that irssi uses a non-trivial amount of margin space as well!
For example Discord is borderline unusable if it is one of two windows side-by-side on my laptop, and completely unusable if you have three. This can't even be an unusual case for people on UNIX derivatives using tiling window managers - Windows has had functionality to tile windows like this since 7. Whatever happened to responsive design? See Telegram desktop client for an example of how it should work - the layout actually changes as you resize the window.
not being able to snap the window seems to be a conscious choice on their part
Yes, I have a terminal (xterm) with irssi running, that terminal is 80x24, and give or take the timestamps, it is indeed between 50 and 70 characters.
Whereas Wire and Riot takes up the entire screen as a single window.