I disagree somewhat.

Most modern difficulty settings are naive, and that is part of what creates frustration.

In learning any new skill, most people don't just continue to do one thing as they get better. Guitarists don't get better at strumming chords, they learn to pick chords, or they go the rock route and learn more advanced fingering techniques like hammer-ons and such, or they learn to use a slide. Most games don't take this into account.

For example, take a game I'd pretty much praise in most ways, Skullgirls.

Skullgirls successfully implements a number of the advanced concepts in the larger Street Fighter scene, like cancels and such, but for some reason they designed a final boss that isn't just unfair (like most fighting game bosses) but actively ignores almost every element of advanced play. Instead, she's just got a ton of health, so the only way to get her down is to have a powerful rush, or a lot of patience.

And like I said--that's a game I'd praise, never mind Call of Duty or other games I would criticize heavily.

There are, of course, some games that do take scaling player skill rather well into account; Devil May Cry and the Souls series both actively encourage advanced tactics, for example. They're set up in such a way that when you start using advanced strategies, it not only gets easier because of the more effective strategy, but also because the encounters are designed to facilitate them.

Except the Gwyn fight, which was totally not set up to be that comically easy when you use parries.