The observable universe is smaller than the objective universe.
If you could instantly transport yourself to the particle horizon of the universe you'd just see a universe that looks pretty much like the one you just left but with a slightly different arrangement of stuff.
The CMB represents the oldest light in the universe from when the universe cooled enough to become transparent, and its traveled so far and long that it's red-shifted from visible light to microwaves.
The further out in space you look, the farther back in time it is.
Thanks to inflation and expansion, the observable universe is bigger than it is old, and things like distant protogalaxies and CMB will eventually redshift into oblivion because the light being emitted from it "Now" can't ever get "here" because the space between them is expanding faster than the light can make up the difference.