I think at least some of what Pat is discussing here could better be called "life skills in the campaign setting". There are often but not always analogous to real-life skills, but ultimately that is neither here nor there. An example is learning to protect your fragile party members. That has real world directly analogous bits, such as "Put your heavy infantry in the middle front, not your lightly armored archers." The presence of wizards and other fantastical elements twists the specifics around, but the principles remain the same. Learning the principles is a form of "skill" in general, call it player skill if you want, but it is applicable to other things outside gaming, such as a study of military history. Learning how to apply those principles to the specific rule set is the real player skill. Learning how to apply those principles as your character in a setting is a somewhat different thing.
The rules are fairly simple. The implications of some of the rules on the setting are often more complicated.
Not quite. Let me see if I can explain it better.
Small unit tactics on a board is a skill. A real player skill. A skill wargamers have, and people new to roleplaying usually don't. Most of the original wave of D&D players had that skill, and didn't even have to think about it, because it was so deeply ingrained. It was how they approached analogous situations. Most of the second wave of roleplayers, the kids who picked up the game in the 1980s, lacked that skill.
But RPGs aren't wargames. It's in the name --
roleplaying game. (Yes, OD&D says miniatures on the cover, but that reinforces the shift, since it's missing in later editions.) The second wave of kids came infused with stories of epic heroes, like Lord of the Rings, or the serial and guaranteed victories of Saturday morning cartoons. Their expectations were based on those stories, so they came to D&D with the idea that they'd play singular role, who would have dramatic immunity, and be rewarded for being a hero. Old school D&D tends to dash those hopes, because it's not built around that. It's built around a wargaming chassis, base motives, and a certain degree of historical realism (though the caveats on the later is an entire essay on itself), and everything that implies. Yes, you can twist the game to be more forgiving and heroic, but you're fighting against the very structure of the game. At best, you can soften a few of the edges. A lot of people ended up playing hybrids, either half-adapting their expectations, or becoming frustrated.
And that's the problem. Expectations. Players from the 1980s until today come in with the wrong set. And that's not a matter of skill, it's something deeper. And that something is very hard to explain in text, because our expectations are largely unconscious. They're not a set of rules, that we can read and easily apply. They're how we think, and how we approach the world. As a result, players (including me) spent decades butting against the rules because our expectations didn't fit. That's why I say player skill is misapplied, because it's not a skill in any conventional sense. It's more akin to learning to appreciate romance novels, or sushi.