You can in fact get something "pretty close" to Positron by adding and configuring a whole bunch of VS Code extensions, adjusting the layout, etc. However it's fiddly and time-consuming work (and quite challenging for novice users); the resulting UX can be pretty disjointed, too.

Positron provides a batteries-included experience that lets you work with Python and R out of the box; it's easier to get started, everything's already set up for data work, and the tools all work together smoothly. At least, that's the goal. :-)

(disclaimer - I work on Positron)