I'm part of the Zoho Writer team (Google docs alternative). And the new architecture is very similar to Zoho Writer i.e edits represented as a sequence of retains/keeps followed by action.

Also the decision to forego browser's selection and draw a custom layer.

All this makes reasoning about changes a lot more saner and intuitive. I've always wondered why prosemirror's transactions & steps couldn't be simplified further so I'm one vote up for the new design direction!