I don't know what the horizon looks like to the naked eye but what's the intent of the photo? As a pleasant landscape, to my eyes, the original looks best. The lighthouse appears vertical with its taper intact and the horizon dips as it would if you were looking down at a horizontal line vanishing behind the observer (sit in a chair near the center of a room and look down at the wall/floor intersection and up at the wall/ceiling intersection.) The cloud base appears approximately horizontal, diverging from the horizon, appearing closer on the left adding depth and motion, especially with the shoreline beneath.
The second photo rotates the right side (it's round, so there's only one side?) of the lighthouse tower vertical, making the entire photo seem tilted even though the horizon is level. The lighthouse wall taper is unnaturally enhanced by the left side appearing tilted to the right, the vertical shadow no longer vertical and the base leaning right. It still maintains well the illusion of depth.
The corrected photo is more orthogonal but emphasizes the foreground and loses quite a bit of depth in all three axes. The lighthouse appears to tilt left and the shoreline on the left appears closer or dropping right.
I once took a great photo of a grove of white birch trunks on the side of a steep golden sunlit grassy hill. With the exception of one tree, all of them were growing normally, straight up with the loner growing slightly to the right but almost perpendicular to the ground. Tilting my camera right so the loner was vertical and the ground approximately horizontal, the resulting image showed a grove of trees all growing tilted oddly left, the one now vertical tree setting the scene. Unless the loner was covered in the photo, it was almost impossible to "see" the artificial tilt that created the photo. Viewers focused on the one straight white tree trunk among the rest, not the slightly sloping ground line.
The same scene with the mass of trees shown growing as they really were was colorful but ordinary.
We tend to use vertical lines as references more often than horizontal lines. In your photo, the white lighthouse would likely be picked up first, then the horizon, then cloud base. If the lighthouse tower looks natural, the rest should follow. In a scene where horizontal elements dominate ( straight on street view of a house on level ground, e.g.) they are more important to have level.