My main thoughts are that I want full control over whether I ever use my reaction or not, in the moment, every time... And you're highlighting one of the reasons why even having a three-way toggle, as palatable a solution over the current system as it may be, is going to come up less than satisfactory at times. The only way it doesn't is if the toggle is universal, rather than individual, and then it can only be flexible enough if set to 'ask' - which puts us back at putting it in the player's hands every time.
To be clear, I'm still for options with a fully fledged reaction system, allowing players to automate it to various degrees if they want to; the three-way toggle is the best way to make everyone satisfied - as long as those options contain full player control, ask me every time, as well.