I find 2x to be too fast for comprehension, unless it a very slow speaker. 1.5x works perfectly fine for comprehension, however.
The human brain can interpret a range of speech speeds. I’m a fast-talking Northerner, living in the slow-talking South, and I often find the pace of speech here to be too slow (and I’m guessing the Southerners around me wish I’d take a breath once in a while).
And it gets balanced out by the fact that I listen to Spanish language podcasts at half-speed because I’m not fluent and find that many speakers are just too fast for me completely comprehend. I do with that Stitcher had a 0.75x speed, though, because 0.5x is a little too slow for enjoyment (and almost hampers comprehension).