FYI There is a great chrome extension that allows you to control playback speed, and it works on just about every video site.
For whatever I reason, I have to use Firefox to watch Disney+. (Mac Safari will always eventually ABEND. Shouldn't Apple regression test Safari on the Top X most popular sites?!)
As for spotty rewind, like with Netflix, another comment might have the explanation (root cause); streams are broken into individually encrypted chunks. So of course there's lag (latency) when jumping around the timeline.