While there’s a kernel of truth to the idea of “planned obsolescence”, it most certainly is a conspiracy theory the way it’s typically presented. Consider the brouhaha about battery health a few years back. Apple throttled the phones so they wouldn’t demand voltage spikes that would cause the phone to reset. Having had a phone that would reset due to battery issues and one that would just slow down, the latter was much more preferable and allowed me to extend the usable life of the phone. That’s the exact opposite of what planned obsolescence would suggest that they do. Does Apple want you to buy new generations of their products? Of course. Does Apple deliberately cripple existing hardware in order to drive new sales? Doesn’t seem to be the case, if anything, Apple bends over backwards to support older hardware.
Look at the iPhone 6/7/8 models and how long they supported them. Certain generations of Macs were continuing to get upgrades for about a decade after their original release. Yet, I don't hear people complaining when Microsoft forces users off of Windows 7 for 10?