Networking surely does introduce complications especially when TLS is now basically considered required and cert lifetimes are being limited for 'security' reasons. However most consumer devices have functionality, often their primary/most important function, to which network connectivity isn't even needed. For instance, a speaker producing sounds.
In the factory reset state, things should have a USB flash drive firmware install route which could be used to bring back working root certs, etc.
Of course again this depends on whether the mfg is worried about DRM bypass hacks that are found later on in the factory firmware.
I'd support legislation to issue stiff fines for devices that can't be factory reset at any time, with the only exception being for directly-consumer-benefitting anti-theft (so, iCloud lock is okay).
