[Jnr]

How come Gnome is not there?

[selkiesproject]

GNOME forces OpenGL 3D compositing with no way to turn off, which is very uncomfortable without a GPU. Every other X11 desktop environment allows to turn them off, which is more tolerable when using llvmpipe, the software CPU Mesa OpenGL implementation.

[doubled112]

While I've never used GNOME inside a KasmVNC session, it used to feel slow on reasonably powerful machines in an Xrdp session.

That'd be my first guess.