You memorize scales by SOUND. That's it.
Loop a single chord vamp, and play the scale over it. Make melodies with the scale, don't just run up and down it.
Eventually, you won't need the shapes, because you will know what the note will sound like before you fret it.
Use the shapes to train your ear first, then in time, your ear will take over and shapes will be forgotten.
Playing laterally, rather than vertically always helps too. It breaks you out of boxes.
So much truth here! I think this is the most important thing. Each scale is unique and conveys a different feeling.