For landscape photography, a tripod is probably the most important equipment you should own besides the camera. If you have a good camera with an expensive lens and you do not use a tripod you will not get the most out of the camera and lens.
The more megapixels your camera has, the more important it is to keep the camera steady. Blurry 24 Mp photos are worse than tack sharp 12 Mp photos.
One of the problems beginner landscape photographers often experience are blurry photos. If they used a tripod, some of these problems could have been avoided. Even with image stabilization you will not be able to handhold your camera if you want to get the sharpest images your camera can produce. The longer focal length you use, the more important this is.
As a rule of thumb, you can handheld the camera as long the shutter speed is not slower than the reciprocal of the effective focal length of the lens you use. If you shoot with a 50mm lens, the reciprocal is 1/50. This means the slowest shutter speed you can use is 1/50 seconds.
With the improved technology of image stabilization, you might get away with a slower shutter speed than the 1/50 second. How well this works is also dependent on you “handhold” technique.