You're about right with the 18% grey, but most skilled photographers do rely on the in-camera metering these days, regardless of which P/A/S mode they're using.
They may not use matrix metering (I definitely don't, I use center weighted, and I'm just a hobbyist) but you also have to remember the dynamic range of a full-frame RAW file is pretty good and that you can get good shadow/highlight recovery out of most situations.
When the photographer is chimping the image post-shot, if they see that the exposure is way off, you can still program-shift the settings in P-mode or use the EV dial to make adjustments and reshoot.
I come from an age when SLR cameras did not even have batteries, leave aside digital sensors. So probably it is hard wired into me that I need to use my eyes and brain and leave aside the cameras' when shooting.