from The American Heritage® Dictionary of the English Language, 4th Edition
- transitive v. To eliminate the need for skilled labor in (an industry), especially by the introduction of high technology.
- transitive v. To downgrade (a job or occupation) from a skilled to a semiskilled or unskilled position.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To redesign (a job) so that less skill is required to carry it out, for example through the introduction of new technology.
- v. To change the role of (workers) so that they are no longer required or able to use the skills that they have acquired.
This combination of de- + skill conveys a pejorative connotation that "simplify" lacks. (Wiktionary)