You've been around this stuff for some time, a uhh member for over 5 years now, and used other equipment enough to probably know that there's something wrong with your lenses, or camera, but you might be able to give them a little better test and answer your own question a little more definitively. Rather than aim the lens at a wide open field, as you have in that image you posted, I'd like to suggest that you perform a more specific test. Get something like an eye test chart, a rifle target, something with distinct and fine lines on it, tack it to a fence a few feet away in good light, with no wind, and do the tripod thing with a remote control or use the 10 second timer rather than the two second, getting some images that you can blow up and see whether or not your lenses are focusing properly. It is often said that many lens are sharpest a couple of steps up from wide open. Don't just shoot at f/8 but rather, try other f/stops and see if there are other stops that give you sharper images than f/8 - maybe from f/4 to f/16, for instance and compare them against f/8. Some people use a newspaper or a magazine cover as targets even. It doesn't look to me like you're giving your lens much of a test, aiming them into a wide open field like that, with no particular discernible subject even though you say you did roughly use the bottom of that fence post as a tentative subject. It certainly isn't all that evident just what you were shooting at upon first glance.

Here's a list of (too many?) focus-checking links. What you have to do is see if the lens is focusing on any plane. It might be able to focus, but not exactly where you want it to focus.

Focusing Charts
http://mansurovs.com/wp-content/uploads/2012/07/Siemens-Star-Focus-Chart.pdf
http://mansurovs.com/wp-content/uploads/2012/07/Focus-Test-Chart.pdf
http://regex.info/blog/photo-tech/focus-chart

How to Check Focus
http://photographylife.com/how-to-quickly-test-your-dslr-for-autofocus-issues
http://www.luminous-landscape.com/essays/are_your_pictures_out_of_focus.shtml
http://regex.info/blog/photo-tech/focus-chart#features
https://photographylife.com/how-to-quickly-test-your-dslr-for-autofocus-issues
http://cameralightlens.com/newsblog/?p=264

Adjusting Camera/Lens
http://www.nphotomag.com/2013/03/05/how-to-recalibrate-your-nikon-dslrs-af-autofocus/
https://photographylife.com/how-to-calibrate-lenses
http://www.canonrumors.com/tech-articles/this-lens-is-soft-and-other-myths/
http://digital-photography-school.com/how-to-do-autofocus-fine-tuning-on-your-nikon-dslr/

What were you actually focusing on? Besides the slow shutter speed everything is very soft EXCEPT for the fence post in the bottom middle which, although not tack sharp, is reasonably sharp. Does your camera have different focus modes allowing you to choose individual focus points or groups of points to train directly on your subject? With traditional mirrored DSLR's when you use all focus points, especially in auto mode, the cameras will tend to focus on the closest object in view, which in this case would be the bottom center fence post. I don't how whether a mirrorless camera like yours would respond similarly, but I wonder if that might be the problem. I'm also not familiar with the shooting modes for your camera. Were you shooting in full auto?

The attached image is Photoshop's interpretation of your image in and out of focus. (Masked area indicates not in focus.)

That which is in focus appears soft.

Your shutter speed of 1/50th may not be fast enough even on a tripod in windy conditions, but another possibility is that there was a very slight movement of the camera when the shutter release was activated. (See how the masked area is a little more pronounced on the right hand side - only the base of the telegraph pole is sharp whilst the upper parts are blurred - and thus masked out. The single sheep in focus is near to the centre of the image.

Use the same lens at f/8, on tripod, stabilisation off, mirror up, remote or timer release. ISO up a bit to shorten the shutter speed and see if there is an improvement.

I can't reconcile your comment that it's a mighty fine camera but you can't get a decent photo out of it. Since the whole purpose of having a camera is taking decent photos, I find it strange that you would say that. The fact is though it is a very very fine camera, and while I have no familiarity with those lenses, chances are it's not the camera or the lenses, but your technique and understanding of how to get the best from this camera that's the issue. Please post one or more of the photos that are problematic. Be sure to check the store original box so we can see it at full resolution.