> How many other devs/teams are going to reasonably take that on?
This strikes me as a sort of devolving-human standpoint that might lead to someone in 2050 asking how anybody could possibly walk 10 miles unassisted.
In the past, small teams of talented developers have written an entire game + game engine + associated tools from scratch, countless times.
Doing in-depth custom UI development for the desktop as part of creating a text editor does not bin as 'Mountain-moving; Don't even try' difficulty.