Why would you be disheartened? A lot of photographers (including skilled amateurs and pros) shoot in P mode when the situation allows for it.
Prolific shooters usually know what to expect from their camera, so there's no need to experiment with settings all of the time, and if they see a P mode choice they don't like, they can program shift or switch to A/S/M mode.
I am not aware of your level of understanding of digital photography, so please pardon me. But as far as I understand, an average camera tries to reach the correct exposure by adding everything up to 18% grey. I am intentionally leaving the metering discussions out here for simplicity. So in case your frame contains too much light and shadows, your metering will be thrown off.
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.
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.
Prolific shooters usually know what to expect from their camera, so there's no need to experiment with settings all of the time, and if they see a P mode choice they don't like, they can program shift or switch to A/S/M mode.