Which is just fine! Vimscript was created to create simple vim scripts, not to build full programs.
And if you need to do more than Vimscript can do, Vim already provides this: it has native bindings to Lua, among other languages. If Lua was such in demand to write vim scripts, at this point it should have taken over VimScript as the main extension language, but it hasn't, and I guess that unless something huge happens in the community, it won't.
Which is just fine! Vimscript was created to create simple vim scripts, not to build full programs.
And if you need to do more than Vimscript can do, Vim already provides this: it has native bindings to Lua, among other languages. If Lua was such in demand to write vim scripts, at this point it should have taken over VimScript as the main extension language, but it hasn't, and I guess that unless something huge happens in the community, it won't.