As far as age is concerned, my own father was one of those COBOL cowboys back in the '70s, but he kept up with the times.
When my father was in his upper 70s, my son got a new computer so he returned the Tandy 1000SX that had made the rounds of the family to me. It had no hard drive, just 360K and 720K floppy drives. I asked my father if he wanted it and he said "yes"--mainly because he had a friend (also elderly) whose daughter had given him a word processor typewriter that she got at a garage sale. This friend was always sending my father letters bragging about his word processor, so I guess my father wanted to go one better with an actual computer. He had never used one before.
The computer ran DOS, of course, and my father used Quicken for DOS to manage his investments and PFS Write for writing letters--mostly business letters but some to his friends. Then in 1996 or so my husband and I took our first foray into serious hardware upgrading and replaced the motherboard, graphics card, and CPU in my computer. We had enough replaced parts to build a computer for my father if we bought a case and floppy drive. He paid for those and we put Windows 3.1 on it for him.
He liked Windows right away and switched to Quicken for Windows, some Works suite for word processing, and Print Artist. He also had us buy him an Epson inkjet. He actually started making graphics things with Print Artist just for fun. Mostly he worked with Quicken. He really loved the computer.
When my father was 80, we got him a modem, installed it, and were about to sign him up with the local ISP. Unfortunately, a couple of days after we got the modem in the computer, my father died suddenly. I've always been sorry he never got to experience the Web because he would have LOVED it. He probably would have been on the computer all day and night. In 1998 the Web wasn't what is today, but with his interests in politics, sports, and his investments, even then my father could have found more information than he would have had time to read.
My mom told me once that some times he would stay up late at night "messing with that damn computer."
My dad did that, too. I was his 24-hour tech support, so it wasn't unusual for me to get a call from him at 11 p.m. saying "I lost the letter I was writing." So I'd ask him "what do you see on the screen?" He'd tell me and I'd have him either close or minimize the window. After maybe four more layers of windows, there was his letter on the bottom of the stack. He also had a knack for getting his files in some odd place like the root directory, so every few weeks I'd go through his files and find the stuff that had "disappeared."
If he were alive today, I think he'd certainly explore Linux and maybe even use it as his main OS. He would be 91. It would never have occurred to him that he was "too old" to learn something new.