Remember that a ryu is a flow from a source. If you innovate too much, you cut off the ryu's link to its divine origins. You also may alter the style so much that it is unrecognizable as that particular style. He didn't hide behind trying to call his altered system Wing Chun, although it appears that he did continue to draw a great a deal of influence from that art. At least he was honest and didn't try to appear what he wasn't.
Innovation is necessary in a sport to further it as a sportive endeavor.
But a classical martial ryu is not just a sport, it is an art tradition, and to maintain its integrity means maintaining its closeness to its origins. A classical ryu is not a classical ryu if innovation makes it totally unrecognizable. Those with a more practical bent may grouse that maintaining classical forms are irrelevant in this day and age. They argue that learning grappling skills in full armor with a classical warrior's complement of light weapons don't make sense in this day and age, and their way is better. Not only is this distasteful, in my own elitist opinion, but such badly thought out logic attacks the very reason the ryu survived for so long.