Francis Cardinal Arinze protested the used of "Do-It-Yourself" liturgies emphasizing that priests should not add or subtract from approved rites. "Liturgy", says Pope John Paul II, "is never anyone's private property."
In separate but related news, a Vatican commission was proposing the outlaw the use of drums and electric guitars in liturgies. I personally think that no drums would be a shame since I know some good worship music that drums is totally appropriate for. I was just reading some psalms which mentioned the use of drums in liturgical worship. But I'm all for ending experimentation and sticking to the rubrics.
Someone should introduce Cardinal Mahoney and his catechetical Broadway Production Masses to Cardinal Arinze. I'd love to hear Arinze's comments and Mahoney's excuses.
Your link is invalid (or just not currently loading right now). I suppose my Pentacostle experience and church is opposite that of what you are describing. I can't imagine my pastor not having full authority to preach on what he wants, how he wants in a manner appropriate for he and his congregation at that moment.
This pertains not to preaching but how the service is conducted. Not that you would agree on restrictions on that, either. Basically the liturgy is a fixed set of approved prayers and no deviation is supposed to be made from that (since you can slip into heresy by doing so, even without meaning to).