I think the point was that it was lean (didn't need 100MB to draw a screen) because it /wasn't/ cross-platform - more tools are cross-platform by default now because it's easy (which leads to the abstractions that give you requirements of 100MB to draw a screen).
Modern software has certainly become abstraction-heavy, hasn't it? It's not just the GUI libraries. Paint Shop Pro was lean and mean because it had to be, the targeted hardware just wouldn't support anything bloated. Not to mention that many copies were downloaded by modem.