Runs slow?
"until the world remembers that natively-developed code runs faster"
Er, 1985 called and want their reason not to use productivity tools back.
In fact there is absolutely no reason in principle that a graphical tool couldn't produce code as fast as native C or even native assembler. The reason people don't use graphical tools, so they never mature to that level, is that a few lines of C translate into an A3-sized diagram, and no-one wants to wrangle an A3-sized diagram. Which is sad, because once you get above the low level to, say, integration of heterogeneous systems over a network, the diagramming approach should win out by a mile.
This is the same reason, incidentally, that most chip makers write VHDL or Verilog instead of making football-pitch-sized schematics. (Ironically, in that case, the people that do use football-pitch-sized schematics do so to get extra speed.)