1152x900 8bit = 1,036,800 bytes on screen

1920x1080 24bit = 6,220,800 bytes on screen

So for starters, a lot of people are trying to push around more, larger, pixels.

Some years ago I did some experiments with the OLPC-XO essentially analysing this exact problem. Modern software on a platform weaker then current Entry-Level.

Analysing the overhead in printing a terminal text to a screen, I found a process that output a great deal of text but >dev/null took 1.5 seconds and tried a couple of different terminals.

    7 seconds using bitmapped fonts 
    30 seconds using xft
    6 minutes 34 seconds using vte (Pango/Cairo)

That's a lot of overhead. You get unicode, scalable fonts and extras but it all comes with a cost. Most of that cost isn't intrinsic to the additional capabilities, but just an accumulation of minor inefficiencies because the result was ok on the machines we were using at the time.