That’s not entirely correct.
Android wasn’t intentionally designed for planned obsolescence. The issue was that when Android was first made, carriers were unhappy with Apple’s strict policy of having an unaltered version of iOS on every Apple phone. These carriers told Google that if they wanted them to support Android, they needed to be able to do their own customization of the OS. The same demand came from phone manufacturers as well, so Google did its utmost best to make Android as customizable as possible very every party involved in producing and retailing a phone.
The end result is that there are pretty much as many versions of Android as there are different models of phones which makes it impossible for most of the companies in the chain to properly keep the OS on the devices they produce or sell up-to-date. Technically it’s possible, but it costs too much money. Apple is in a different boat, because they produce their own devices so iOS only needs to be adapted for that limited variation in hardware. Android runs on thousands of different hardware configurations.
While from the consumer’s point of view, this can be regarded as planned obsolescence, it wasn’t initially intended as such.