What are you talking about?
OS X.11 El Capitan's compatibility list:
That's eight years old or newer Macs are being supported with the newest OS X iteration, where's the "planned obsolescence," ErnBatavia? The older Macs still run on the older OS X. If they cannot run OS X El Capitan, it generally is because they lack the hardware to do so, not because Apple is deliberately locking them out. They just physically lack the ability to run some of the important upgrades in the newer version.
I have clients who are quite happily using ten year old Macs. . . they work, so they are not obsolete.
A new version of their “phones” every few months smacks of planned obsolescence to me....