I'm 60 years old, and while I'm somewhat unusual in that computers and tech have been part of my life, both personally and professionally, for half my life, I would have to think pretty hard to come up with someone in my circle of friends and relatives in the 50-80 age range who doesn't use the Internet. My 80 year old aunt has a desktop, an iPad and an iPhone. My 81 year old landlady spends an average of 4 hours a day online. Just examples.
We could debate their "expertise" in using the Web or software/apps in general. On the whole, given the kinds of questions I end up fielding from them and others, it isn't particularly high. But then again, that may actually be the fault of the software itself, much of which is difficult for someone for whom tech is not an abiding interest to understand. I spent 10 years reviewing software full-time, and it was often a struggle for me to forget what I knew and judge it from the standpoint of the average Joe.
At any rate, I think it's a canard to say that older adults (or even senior citizens, since I guess I am one now) don't use the Internet. They may not use it the way someone younger does, but that doesn't mean they don't use it.