"Quick Reply" has one small advantage, that is one can scroll up to look at previous posts in the same thread while composing. Now it appears that "Extended Reply" also has something like that, but one scrolls down to see that (or so it appears). I guess if "Quick Reply" brought that about, or drew it to my attention, it can't be all bad.
Quick Reply must answer someone's imagined need. It doesn't seem to be a good fit for me, in practice.
One Example: The loss of the transparent ability to respond to a specific prior post by clicking the small black and white "Reply" at the bottom of that particular post is a serious ergonomic slowing.
Thanks for your attention and sustained efforts,
Longview