Various thoughts on this:
•In computer-land, one must always be thinking and moving ahead, operating at least within a few years' timeframe of the latest offerings. Technology is not going to stand still, whether it really needs to move ahead or not. Linger too long, and you are locked out of using the latest software goodies. Of course, it all depends on what you are doing, maybe you can get away with legacy hardware/software (word processing? Image retouching? Video editing?)
That said, I don't want to be overtaken by the Internet Of Things and get my car or refridgerator hacked, so there are some areas where you might be wise to opt out.
•Re: Mac vs. Windows: Build a Hackintosh, use 3 different OS's on the same box if you want to. Keep the macOS license happy by using an old Apple G5 case ("branded Apple hardware"). Not that Apple seems to care anyway, so long as the App Store works ;-). I have a 2011-build i7 Hack that I bought from a friend and tweaked a bit (more RAM [16 gigs], updated from Snow Leopard to El Capitan, added Windows 10, gave up on Linux for now since I don't really need it, though it's nice to have the option). It's the fastest computer I have (even with HDD drives), though it's more of a fun box and not my main gig.
•Re: Old scanners. Use VueScan (
www.hamrick.com). It supports all sorts of new and ancient scanners