A tradition involves the passing-down of information from one generation to the next.
The knowledge is treated as a time-honoured, unchanging standard. 
With kung fu, people have passed-down the art for centuries. But it has not remained static.
To a certain extent, it has evolved with the times.

Is this a bad thing?

Consider: if a 21st Century person was given a 16th Century martial art, would it have any real world value?
If you are honest, some aspects of the art would still be viable, but other material may be hopelessly antiquated.