So many people have different capacities for work and need to apply more effort to reach the same volume of output. There's no fair compensation for the effort as the only thing that matters is output. If a person can't reach output quota, that person essentially regarded as a burden on society. Unemployable by effect that they'll never be as good as their peers.
And the matter is so many people have hidden disabilities, but they go undiagnosed. The pathway to diagnosis is a complicated and long drawn out processes, and those who cannot make it through the process happen to be the ones who are severely in need of diagnosis. There's a catch-22 for you.