In the U-2 everything, everything, was sacrificed for two things, endurance and altitude.
The aircraft wasn't easy to fly at any part of it's flight envelope, takeoff, climb, level flight, descending. Why should landing itself be any different ?
Early in it's development 3 pilots were killed in takeoff/ and climbing incidents.
When the camera that was to be used on the U-2 was being developed , the designer needed 6 more inches of space for his camera. 6 more inches couldn't be found in the fuselage. He had to redesign his camera.
Spoilers would have added weight that they didn't want to add, the controls would have took a little room in the wing that they didn't want to provide for.
3 U-2Gs were built, they had a reinforced landing gear, arresting hook, and spoilers. Plus the U-2H is called carrier capable.