I definitely can feel the lag in normal usage, and it's stressing me. Having tried various terms, I've always quickly returned to xterm with bitmap fonts - even before I'd heard of latency measurements being done on terminal emulators. xterm feels almost instantaneous. Gnome Terminal, for example, always felt sluggish. Not having done any measurements I couldn't tell what it was (and didn't think that other terminals could possibly have noticeably slower latency) - and I still think there can be other contributing factors, like usage of Vector fonts and aliasing. Or, as someone else points out, it might be more jitter than lag.
I also never liked GNOME 3, and suspected it must have something to do with it being a compositing WM and the latency it probably adds on top.
Between Windows, macOS, and the major Linux desktop environments, practically no one is using a non-composited desktop these days.
Compositors tend to aim for 60fps, because that's what most displays can handle. That means you _start_ with 16ms worst case latency on the output side.
You can use one of the many bare-bones window managers to get rid of compositing. I still use xdm and only recently switched away from icewm (because of bitrot) to openbox.
Here I am too. I stick to dwm, currently migrating to wmutils because portability, no compositing on my side. Firefox is the only GUI program I use (besides st), and it will probably remain as such since the web has become a chaotic and complex environment, unusable without a major web-browser.
I also never liked GNOME 3, and suspected it must have something to do with it being a compositing WM and the latency it probably adds on top.