The humble Oly 9-18 still surprises me sometimes. I had one back in 2013 with the original E-M5 and loved it then...sold it when I took a detour to Fuji/Sony/Nikon...and purchased it again used for around $250 last year when I jumped back into OM System.
I think about getting one of the better, and much more expensive ultra-wide options from time to time, but for what I use it for, it just gets the job done! I used it this weekend quite a bit in conjunction with the internal ND filter on both the OM-1v2 and OM-5, and was always happy with the results.
Overall, these are pretty good photos, and it's a shame when the equipment lets you down. It's even stranger when the OP chooses to ignore it.
I apologize in advance for opening the photo full-size; this is the sharp area, while everything else is blurry. Perhaps this was taken handheld? In other photos, the edges are far from perfect, but not as bad as this one.

Douglas Falls | W.V.

Elakala Falls | W.V.
Yup, I totally agree about the edges not being sharp. Luckily, I stopped being a pixel peeper a long time ago and try to take the image as a whole. That's not to say that image sharpness isn't at all important to me, but the overall quality of the picture (to my eyes) for its intended use is what's most important.
I hike, bike, and backpack with my equipment, and there are a lot of non-imaging qualities that also come into play with my choice of lenses and cameras.
Thank you for not taking offense at the criticism
I've used many lenses, and unfortunately, one of the worst was the Canon 16-35mm f/2.8, which produced very similar results. I couldn't put up with this and soon sold it.
You're not the only one on the forum who says they don't examine pixels in photographs. Coincidentally, for some reason, this statement has become very common on this forum.
It's good if you're happy with the result.
Whether the lens is to blame, or whether it's also due to handheld shooting and a live ND filter, only you know.