One thing I'd also like to develop / wish was integrated into audible and the like is silence trimming. Some speakers leave outsized pauses in their narration which can be significantly shortened effectively increasing speed with less distortion.

I have the opposite problem where I have trouble paying attention to an audiobook at 1x. I get bored in between words and my mind wanders making it very difficult to keep track of what is being said (as in I hear individual words but have trouble keeping sentences in memory when everything comes too slow)

I wish I had realized this in university and had been able to somehow record and playback lectures at 2x. I always got so little out of lectures because the information wasn't coming in fast enough for me to process correctly.