It wouldn't have been the primary. The Newton had an on screen keyboard like products today. Innovation is only innovation if it works, and the Newton had a lot of amazing things going on, some of which the iPhone doesn't even attempt. The emphasis on handwriting recognition killed the product (along with a healthy does of hatred from Steve Jobs).
It really didn't kill the product - Jobs did. Yes, the Newton OS had some great stuff in it - I loved the soup model, but in terms of a newspaper or billboard ad? The handwriting was a no-brainer. Yes it was mocked - in much the same way that Siri is mocked today, but with small adjustyto your native handwriting written input became fast Nd accurate
It was mocked before on national tv when national tv was still a thing. It killed any hope for that product. It was mocked on tv, comics, and everyone who did a review. Heck, the Simpsons mocked it long after. It had plenty of billboard quality features (the intelligent stuff was practically built for ads) much more than its simpler, limited competition.
