There two factors here:
1. Our own subjectivity - if I were to compare my older Taylors to my newer Taylors, my description would be the reverse of the OP's description. It has been said that the Taylor signature sound has always been brighter ("brilliance" and "zing" are alternate terms in use) and more balanced than, say Martins. That's why (IMO) Taylor did make changes to create guitars that would feature more bass, volume and depth (again, depending on the individual listener's ear) to address the unfavorable comparison to more traditionally built guitars. Today, Taylor simply typifies what is termed a "modern guitar sound".
2. The changes themselves - modifying each shape, adding the relief routing to the top, CV bracing, etc. all contribute to a modified Taylor sound.
With all this said, I happen to like both my older and newer Taylors. While they all carry a signature sound and feel, there are differences that appeal to my different moods on different days....