KO's are not the new azalea because they are too different. Azaleas tolerate much more shade and bloom in the spring, whereas KO's survive in the blazing sun and are primarily summer color. They cannot be used interchangeably.

Agree 100% - Apples and Oranges.
The grow in completely different conditions.

azaleas: needs some shade. Evergreen varieties will be green or bronze in winter. New repeat bloomers will have a nice rebloom in fall if it gets a good bit of direct sun.

Knockout roses: Likes full sun, though will tolerate some light shade. Blooms almost continuously from early summer to frost. Bare in winter.

You can use both, one for shady areas and the other for sun. Evergreen has advantages.

FWIW I don't think every azalea actually needs shade north of the DC suburbs, I have a couple in full sun, but the only place all of the Encores are hardy is well south of there. I'm still rather irritated I paid top dollar for one of them from a fancy Baltimore area nursery - one of my few purchases of trees or shrubs from a non-specialist, local nursery - only to have it die at a very high winter temp, around 10F. Most of them should never have been rated zn 7 hardy, the species they used to get the late blooming was a very tender SE Asian one. It was the orange one...some of the pink ones might be a bit hardier but I know I've read other accounts on the web of their hardiness having been overstated during the initial launch.

Remember all knockout roses in the eastern US, at least, will probably eventually die of RRD.