“Rules for rules”. To me one of the biggest drivers of system complexity and bloat is “rules for rules” ie—new mechanisms to modify original rules or to make work-arounds to disliked rule restrictions.
Let’s use “Transcend Armor” as a perfect example. Why do we have “TA” as a skill? Because the addition of Paladins and other new professions in RM Companions required a mechanism for Channelers to cast spells. Why? Because the common trope of Paladins is that they are armored knights that cast clerical style spells. The solution? A new skill and a whole bunch of arbitrary new rules so Channelers (or Essence casters) could safely cast spells while wearing metal armor. Let’s ignore the fact that many fundamental rules that we don’t question are really just a result of acceptance to early D&D standards. Why is there a restriction on armor? Because in D&D magic users weren’t allowed to wear armor. Period.