"any highschool kid can go ahead and just build it"
What high school did you go to where everyone was an expert on multithreading, network io, disk io, bidirectional synchronization, and state persistence?
"I know I could probably whip together a decent email client in C++ within a couple months from scratch and maybe a week or two if I used any number of libraries out there."
Want to know how I know that you've never written an email client?
CefSharp (.NET Bindings): https://github.com/ataranto/CefSharp