When you grow to 7 foot tall with 17 inch hands maybe you could answer that question..
It is obviously a reasonable excuse but Yao Ming hit 83% for his career.
Other than Durant who shoots about 90%, these guys are all over 6'10:
- Dirk Nowitzki, .8782
- Jack Sikma, .8494
- Mike Gminski, .8431
- Bill Laimbeer, .8368
- Keith Van Horn, .8346
- Yao Ming, .8328
- Andrea Bargnani, .8243
- Christian Laettner, .8205
- Kevin Love, .8147
- Tom Chambers, .8075
The FT is shot with the fingers and finger tips, if players are putting 17 inches on the ball then they just were not coached well.