macOS Mojave will drop support for some older Macs released before 2012
Fewer people will be able to upgrade to this fall's macOS Mojave, which has tightened the minimum hardware requirements needed to install and run it, according to release notes from the developer beta.

Whereas High Sierra will run on many Macs from 2009 and 2010, the oldest Macs supported by Mojave are 2010 Mac Pros with Metal-compatible graphics cards installed. Otherwise the cutoff is typically 2012, and in fact no basic MacBooks are supported prior to 2015 models.
The complete compatibility list includes:
Some other signature features of Mojave will include a long-demanded Dark Mode, stacked desktop icons, and a Gallery View in Finder. Several previously iOS-only apps are coming to the OS, such as Home and Apple News, and the Mac App Store is being redesigned in a manner similar to its iOS counterpart.
iOS 12 -- also coming this fall -- will support all of the same devices as iOS 11, going as far back as 2013's iPhone 5s.

Whereas High Sierra will run on many Macs from 2009 and 2010, the oldest Macs supported by Mojave are 2010 Mac Pros with Metal-compatible graphics cards installed. Otherwise the cutoff is typically 2012, and in fact no basic MacBooks are supported prior to 2015 models.
The complete compatibility list includes:
- MacBook (Early 2015 or later)
- MacBook Air (Mid-2012 or later)
- MacBook Pro (Mid-2012 or later)
- Mac mini (Late 2012 or later)
- iMac (Late 2012 or later)
- iMac Pro (all models)
- Mac Pro (Late 2013)
- Mac Pro (2010 or later with Metal-compatible GPU)
Some other signature features of Mojave will include a long-demanded Dark Mode, stacked desktop icons, and a Gallery View in Finder. Several previously iOS-only apps are coming to the OS, such as Home and Apple News, and the Mac App Store is being redesigned in a manner similar to its iOS counterpart.
iOS 12 -- also coming this fall -- will support all of the same devices as iOS 11, going as far back as 2013's iPhone 5s.
Comments
Seriously though, I bet its because of Metal and Apple dropping support for OpenGL/CL. Thats still a good amount of Macs that support this new version of macOS...some as far back as 8yrs ago, going on 9yrs by the time macOS 10.15 its released.
If you're someone who uses an older Mac you have to know there will eventually be a cutoff where your Mac is no longer supported. Its the chance you take by continuously using an older Mac.
And its not like your Mac just stops working just because you're not using Apple's latest version of macOS. You can still easily use your Mac with High Sierra for at least 2-3yrs if you choose to do so.
obsoleting Macs that are only 3 years old?
Though im not personally affected by that, it’s wrong. Very wrong.
I dig Mojave. Love how they are making it more compatible with iOS without merging the two, etc.
but... computers 6 years old and newer need to be able to upgrade.
Apple itself defines the timeframe of an obsolete computer and they aren’t even following their own protocol here.
i guess this is the Mac version of the iPhone 6/ios11 “batterygate.”
It will likely help nee macs to be purchased. But it’s wrong. And that’s coming from a long time Apple evangelist.
I just don't like the direction of non upgradeability of the macs now. Apple prices their stuff on the high end. It is good hardware, but I don't consider it to be the best. Basically, I have to pay a premium just to do iOS development. Oh well, such is life.
I fail to understand why Apple would remove the capability from the user, to upgrade the Mac Mini, when this was BUILT INTO this platform, from the beginning. Steve Jobs created the Mac Mini to give the budget conscious consumer, a low-cost of entry into the wonderful world of Apple, and Tim Cook as done everything in his power to poison this wonderful little device.
Tim, stop poisoning the well. It's counter-producive, and it's not winning you any new customers.