As Anton said, the Tango is a bit standalone in the ballroom dances as it doesn't have swing or sway or rise and fall. The method of walking is completely different. It is often taught to beginners, in the same way as cha cha cha is, but both dances have a similar problem in that, whilst it is easy to get started with the dances and learn a routine, it is more difficult to make them look good enough to impress an audience.
In the case of tango, it is the delay and sharpness in the movement of the legs and feet that is difficult. What often happens is that people either don't get it or they also arrest the movement of the body as well which makes the dance look clumpy. There's a specifc technique to the staccato action. Add to that side leads, contrabody movement position and use of the inside edge of the foot and dissociation between hips and upper body. And those are just the basics!