It's true that there's no feature that directly corresponds to parshape. (This is what the ill-fated CSS Regions spec was for; the problem with it is that it was far too expressive to the point of becoming near-unimplementable.)

However, I believe you can simulate parshape by just stacking line-sized floats on top of one another and using clear to stack them vertically. This should give you just as much expressivity as parshape.

See this jsfiddle I threw together quickly (floats in blue to show how the technique works): https://jsfiddle.net/vve89j06/4/

Rectangle vs circle isn't the point of this thread, as I understand it. It’s that the calculated width of text determines the width of a float when the float has no specified width. Here is a fiddle demonstrating what I understood people were talking about regarding floats, although it is a different thing than the other jsfiddle in this thread is showing: https://jsfiddle.net/1wj3efkm/

Also, everything on the web is a rectangle, but that hasn't stopped people from hacking around this (https://meyerweb.com/eric/css/edge/slantastic/demo.html), and there is even a draft web standard to give shape to text (https://drafts.csswg.org/css-exclusions-1/), but only Microsoft has implemented it (https://caniuse.com/#feat=css-exclusions).