QWERTY was not designed to slow you down.
The popular story says the keys were deliberately spread awkwardly so typists would go slower and the typebars would not jam. That is not supported. The layout was meant to speed typing up; the likely influences are letter-pair frequencies and feedback from telegraph operators, for example on keeping E and R adjacent.
Useful: When an explanation sounds too tidy, it was often invented after the fact.
Source: en.wikipedia.org