The technique is generally faulty with "blurry" images 99% of the time with someone new to interchangeable lens cameras (ILCs) with only a low cost kit lens.
The lens is do not the problem. Low-end kit lenses are limited, and they're cheap, and there are much nicer lenses, but How? 'Or' What using one is more likely to be the fault than what the glass is in the lens. People will often blame the goal because they assume a basic mastery of the technique, or because it's just easier than wondering if it could be a lack of knowledge / Expertise, and because there are so many discussions online where people are disparaging the modest purpose of the kit. But kit lenses are surprisingly good, especially for the cost, if you know how to use them. All you have to do is look at any Kit Lens challenge to see it.
Here are some issues that you need to fix, because some or all of them could be involved in your images.
Getting started technique
Nine times out of ten when I see someone shoot with an ILC, they don't hold it properly. If your left hand is cut around the left side of the lens, the little finger closest to your subject, you are wrong. You want your left hand to be cut under the lens / body, palm up, with your little finger closer to you. You can still use the lens rings with your thumb and forefinger in this position. And now your left hand is strengthened to support the full weight of the camera / lens, rather than having the camera hugging your right hand. This is a much more stable grip which allows you to use slower shutter speeds.
Extremes of openness
Openness is an act of balance. On the one hand, the more the lens is open, the more light you get, and the lower your ISO setting and the faster your shutter speed can be. However, any lens used wide open is at its weakest point. Most lenses work significantly better when stopped 1-2 stops from a large aperture (the EF 50mm f / 1.8 II is particularly guilty of this). Chromatic aberration, vignetting and smoothness can all be improved simply by not using the lens at its maximum aperture. A ton of your photos with your 18-55 are 55mm, f / 5.6. Stop it at f / 8, and you will see a little more sharpness. And using too small an aperture, especially with today's pixel densities, can also see diffraction softening things up. So it's probably not good to use apertures smaller than f / 16, unless you have a good reason to do so.
In addition, not shooting wide open gives you more depth of field, which gives you more latitude with the precision of the autofocus. A 50mm f / 1.8 II at certain distances from the subject, if it is wide open, gives a DoF which can be measured in millimeters. Any slight movement of the subject or the camera may cause the focus to drop. Exchanging a background blur for better focus is often worth it.
This is not as common a cause of blurring as most people assume; the first assumption that most newbies do whenever something is blurry is that it's a focus problem. But when you let the camera's autofocus system take over, the problem is that the camera is not smart enough to know what the subject of the camera is ; image and focus on it. Learn the different autofocus modes (such as face detection and automatic eye focus) and when to use them, how to select points or areas of autofocus, how to track autofocus and how to half press and recompose your weapons, here.
If this is a focus issue, check the rest of the frame to see if anything else was in focus. With your wave planes, you will notice that sections of the waves are sharp and perfectly focused, while other parts outside your depth of field are not. If you had stopped at a smaller aperture (for example, f / 11), more of the wave would have been in focus.
Also, don't expect miracles in low light. Cameras need more light to "see" than your eyes. It is normal for autofocus systems to hunt in dark conditions. Your flash can send more light to help focus, or you can use live view and 10x magnification (if your camera is on a tripod) with manual focus when autofocus failed. Pay attention to the "green dot" AF confirmation in the viewfinder.
Minimum focusing distance
If you're from the world of P&S cameras / smartphones, you probably don't know that most lenses can only focus so close (that's why macro lenses exist). Small sensors mean just as small lenses, with very short focal lengths, which is equivalent to a very large DoF, and very good near focus capabilities. When you switch to an APS-C sensor and your lenses get proportionately larger, this minimum focusing distance also increases. The EF-S 18-55 cannot focus on anything closer than 25 cm. Your blurry close-up demonstrates it. You would need a poor man's macro lens or macro methods (close-up filter, extension tubes, inverted lens) to take a closer look.
Shutter speed too slow
Shutter speed can affect you more if you use a longer lens, but even with IS, there is still a lower limit, and that assumes you have a good grip technique to start with. If you're shooting with one hand, if you don't know how to stall your feet or time your breathing, you'll need a faster shutter speed. 1 / 30s is a typical threshold, and there is a basic rule of about 1 / focal_length or faster. Some people would multiply that by 2, or also add the crop factor. @ 55mm, this would mean using a shutter speed of about 1 / 100s or faster. And it is with a stationary subject. With a moving subject, to "freeze" the movement and avoid blurring, you may need an even higher shutter speed, and the height depends on the speed at which your subject is moving.
Also consider using physical stabilization for very slow shutter speeds: a tripod, monopod or beanbag can make a big difference. Plus, for macro shooting, everything is magnified – camera shake or subject movement included. 1 / focal_length may not cut it the closer you get.
Pixel post-processing and optimization
Don't take a look at the pixels to judge the sharpness, unless you are a lens tester :). Look at the picture as a whole. Asking for perfect perfection like a razor on every pixel of an image is a big and big question. Very few lenses are up to the task, and certainly not a kit lens used wide open with poor technique.
Also be aware that P&S cameras, smartphone apps and most photographers improve the sharpness / contrast / saturation of an image through processing. Don't expect JPEG files directly from the camera – unless you have asked the camera to add these – look as sharp / contrasting / saturated as web images that were taken in RAW and post-processed with care and competence. .
See also: Why am I having trouble getting accurate results with my new DSLR …?