To expound on this comment: SDL1 defaults to fully software rendered output. You can hack in opengl hardware rendering, but it's fairly common for SDL1 games and such to be fully software rendered and run fine.
SDL2 in general is hardware rendered.
SDL1 is a good counter-example to "software rendering isn't quick enough anymore". You can make perfectly performant 2d games with sdl1's software rendering... 3d, not so much.
People usually use SDL1 with OpenGL, and I don't understand what part of it is "hack". Is using OpenGL with a manually created context with tens of platform ifdefs less hacky? Or is EGL/glut/<your favorite wrapper> the one true way of doing things?
It's not a hack in that it's held together by tape, precarious, or any such thing; it's a hack because it's going around the back of SDL to do the graphics, even though SDL is supposed to do all the graphics for you.
Perhaps my wording was poor. It's more of a hack than in SDL2, where all the SDL functions support hardware rendering with no need to touch OpenGL directly ever.
The general point still stands that you can write performant software rendering in SDL1.
SDL2 in general is hardware rendered.
SDL1 is a good counter-example to "software rendering isn't quick enough anymore". You can make perfectly performant 2d games with sdl1's software rendering... 3d, not so much.