The point is that the god-crafted eternium lock is no harder for you now than the rusty bronze lock was at the start of your career. i.e. you have to roll a 15 for both...you have a 30% chance to pick the rusty bronze lock at level 1, and a 30% change to pick a god-crafted eternium lock at level 20. Why is this a problem?
You do get better at things, just by a different metric: the number I have to roll against a level-appropriate challenge doesn't necessarily change, but the level-appropriate challenge *does* change, so my skill *does* show. An untrained thief could *never* pick a god-crafted lock...but I'm skilled enough that it's as easy to me as a good iron lock is to the average thief. That speaks volumes about my skill (IMO). Would you disagree?