Following the end of its WWDC 2021 keynote, Apple published preview pages for macOS Monterey and iOS 15. Those include a list of all the devices the two operating systems will support once Apple releases them to the public later this year. And when it comes to the latest version of it desktop software, the company plans to drop support for many of its older computers.
To install macOS Monterey on your computer, you'll need a late 2015 or later iMac, a 2017 or later iMac Pro, an early 2015 or later MacBook Air, an early 2015 or later MacBook Pro, a 2013 or later Mac Pro, a late 2014 or later Mac mini or an early 2016 or later MacBook.
By contrast, you can install macOS Big Sur on a 2014 or later iMac, a 2017 or later iMac Pro, a 2013 or later MacBook Air, a late 2013 or later MacBook Pro, a 2013 or later Mac Pro, a 2014 or later Mac mini or a 2015 or later MacBook.
In short, outside of the iMac Pro, most of Apple's lineups lose some form of support. It's most drastic when it comes to Apple's more consumer-oriented lineups. As you can see from the list, the MacBook Air and MacBook Pro families include several years worth of models that won't get access to Monterey, even though many of those computers may include the same or more powerful hardware than the late 2014 Mac mini that made the cut.