I’ve got MS and QTEs are really problematic for me. Stuff like in the BF3 Coop is ok (single key presses), but I cannot play NFS: The Run without my wife doing the QTEs for me as I cannot do the rapid keypresses.
JohnnyK, via RockPaperShotgun

Button mashing can be seriously painful. If you’ve got to button mash to, say, open a window, or beat a QTE, that’s kind of aggravating. It’d be nice to have an option to hold a button down instead.
cyusha, via Reddit

The only things that should be mashed are potatoes. Button mashing is my nemesis.
Erin Hawley, via Twitter

These require rapid precision, which for gamers with a wide range of strength, fatigue, pain, speed or accuracy related impairments can be a huge barrier or even exclude completely, especially in the case of quick time events where the level of accurate timing required is increased dramatically.

If you can’t avoid QTEs or button mashing actions, include a setting to simplify or skip/disable them.

Best practice example: Uncharted 4
Best practice example: Castlevania Lords of Shadow 2
Best practice example: The Witcher 2