I think I have a pretty low tolerance as well.
I can say I find the CVS machines slow the few times I’ve used them. Possibly Home Depot too but I have little experience.
But at Target, Whole Foods, and two local grocery chains it just hasn’t been an issue.
The UI is slow if you need to enter a code for a vegetable or when you hit pay, but for scanning it works fine if I ignore the slow prompts and just go at a comfortable speed.