I've not done a huge amount of stitched panoramas in my life, but have found them to be not too problematic until now.
I was road testing my new Canon TS 17mm and thought I'd womp together a stitched pano at a nearby swamp to see how it'd look.
See attached, and notice the two distinctive bumps on the horizon line. The power lines to the right of the nearest tower are also very mis-aligned.
I was reasonably careful when levelling the tripod head.
Any clues where I let this one get away?
Hard to say, because of the black-box approach of Photoshop. In my experience, which is extensive when it comes to Pano-stitching, Photoshop can do an okay kind of job, as long as the input is not too problematic/challenging.
Input can be problematic if there is no EXIF data, or the images have been cropped or distorted before stitching. Photoshop can also have a problem with Tilt and Shift lenses, especially with when shift was applied. Also when there is very little overlap between the images and they were not rotated through the axes at the location of the entrance pupil of the lens, it may be impossible to align both foreground and background detail.
A dedicated stitching program should not have too much problem with most of that, and even leveling should not be absolutely necessary, also because the program would allow to manually tweak the parameters that need to be used to get a better result. Photoshop doesn't allow adjustment of parameters, so if it works it works, but if it doesn't, you're usually stuck. All that then remains is editing with e.g. the Warp tools.
If the problem you experience is caused by missing EXIF data, you could try and paste a copy of the image in an image that has the same camera settings, especially knowing the correct focal length is important for stitching. If the problem is caused by (some of) the images having shift applied, you can pre-process the image tiles by adding some transparent
Canvas space to each one of them, enough to vertically center the real horizon in each image.
For problem images, you could also try a free very capable dedicated stitching program such as Hugin, which does allow lots of manual intervention. It can also use better resampling algorithms than Photoshop, and that will produce sharper output.