If LR can do "Auto Tone", why can't it do "Auto Straighten"?
And if it can do "Auto Straighten", why can't it do "Auto Keystone Correction"?
I have a few hundred images shot over water (across Juan da Fuca Strait, and on the Oregon coast) in which I've had a very difficult time determining exactly where the horizon is because of large waves, mist, fog, distant cloud, etc., but these are easy compared to a scene shot across a lake. (I've adjusted some of them several times).
In the case of an image shot over a lake where the far shore is not perpendicular to the line of sight and the camera is not at water level, it is impossible to visually
determine a horizontal line on the image because there is none. If one knew the angle between the far shoreline and the line of sight, and also know the angle between the lake surface and the line of sight, it is mathematically possible (with three dimensional geometry) to calculate a horizontal. There is still the problem of determining the first angle (angle of shoreline to line of sight) - I have not found an easy method of doing this.