Not mellow yellow. blurry, out of focus, or what? 10-24mm w/X-T1

Without repeating too much of it...

Diffraction:

Most lenses are sharpest at around F5.6 then get increasingly blurred by diffraction. F13 is way past the point where it will destroy detail.

You only need to stop down to get higher depth of focus with long lenses, or if there is lots of detail in the near foreground. At 24mm this shot could easily be taken within the optimum range of F4 - F8, probably at F6.3 or F7.1. There is no need to go higher in this case.

Highlights:

There does seem to be some highlight clipping, but this will happen when you use high ISO. Increasing ISO reduces the dynamic range of an exposure (1 stop for each doubling in ISO). The information that is lost is always in the highlights.

The full capacity of the sensor (maximum dynamic range) on the Fuji occurs at ISO200. Always use this for daylight shots unless you absolutely cannot get a fast enough shutter speed. Use a tripod or IOS if necessary.

In this case, you have lost 2 stops of highlight information, hence the channel clipping.

Advice For landscapes:

Shoot in Aperture priority mode. Control the depth of field before anything else. Use the lowest aperture possible that achieves required depth of focus, in other words the nearest and furthest objects you want to include should remain in sharp focus.

If in doubt, stick to F6.3 for very wide (10-20mm), F7.1 for wide (20-30mm), F8.0 for normal-mid tele (30-50mm). Also, focus somewhere between the two extremes. This should maximise the DOF for a given aperture.

Let the shutter speed fall where it may. Use a tripod or IOS if the shutter speed is much below 1/2X focal length (eg 1/100 for a 50mm lens). You do not need a heavy expensive tripod for Fuji cameras. (This advice does NOT apply to action or sports photography, or anything moving...)

Always shoot in the lowest standard ISO setting for daylight shots. On Fujis that is ISO200. This will give you minimum noise (more detail) and maximum dynamic range.

Check the histogram in the viewfinder and adjust the EV comp dial to avoid bunching the exposure to the right. If you use a low ISO, you can always recover shadows in post processing, even with JPEGs. You cannot recover highlights.

Workshops:

Best thing I ever did (many years ago now) was go on a 5 day workshop in Spain. Not only a lot of fun, but very instructive with immediate feedback and critique. Was also a very nice vacation.