Product segmentation probably

Incompetence.

Of the management maybe, but it's not like the Intel staff who managed to pretty much stay competitive with the cutting edge despite them being stuck on 14nm for years forgot how to design a memory controller.

Make that market segmentation instead.

Intel intentionally limits consumer grade hardware in order to create distinct market segments - from overclocking to memory support and PCIe lanes.

True, but that kind of mismanagement is what caused Apple’s migration to Intel in the first place. While it made sense for IBM, losing Apple made no business sense for Intel, as Apple was a valuable showcase partner.