There's not really such a thing as usability that benefits everyone. Design is defined by tradeoffs; if you think you've found a perfect solution, you probably haven't fully understood the problem.
Many blind people rely on tactile paving bumps to navigate the urban environment. Those bumps are a literal pain in the ass for wheelchair users who have to roll over them. An ATM that is low enough for a wheelchair user to reach might be too low for a tall person with a stiff back. A computer interface that seems absurdly over-simplified to a power user might still be impossibly complex for a novice.
Many blind people rely on tactile paving bumps to navigate the urban environment. Those bumps are a literal pain in the ass for wheelchair users who have to roll over them. An ATM that is low enough for a wheelchair user to reach might be too low for a tall person with a stiff back. A computer interface that seems absurdly over-simplified to a power user might still be impossibly complex for a novice.