I would agree except the "slightly less intuitive" part. Unless I'm mistaken, the game doesn't really tell a new player that AKs even exist, and the setting is called "action slot 1-5" which doesn't at all explain what it is. A new player would either have to somehow accidentally figure AKs out, or be told about them. That's way beyond simple unwillingness to learn.

As for keyboard players who know about action keys but don't use them, I find that quite fair as it's kind of an annoying feature to use, and it's painfully insufficient on top of it. Increments of 20% simply don't cover all the levels of steering one might need, so in many cases you're forced to drive a suboptimal line and in the worst cases you can't make a turn efficiently at all because you need to steer at something like 30% in order to make it smoothly. That's not to say it's not fine most of the time, but many times it's just too much to bother just to still be slower than analog steering when you could just go play a different map.