This is why auto-sliding sliders with text are always a terrible idea. You can never sync them to all users read speed, so some always think they are too fast, and some always think they are too slow.
My honest advice would be [1] and it should be designed in such a way that all reviews are visible, perhaps in 3 columns, instead of a stupid carousel slider. But slowing down the slider would be more trivial - as I expect very few people are actually able to read all of the text of any of the excerpts before it changes on them.
[0] https://www.w3.org/TR/UNDERSTANDING-WCAG20/time-limits-pause...