[RetroTechie]

> maybe my hope is misplaced and many-contact connections will always be worse than direct attachment

As much as I like socketed / user-replaceable parts, fact is that soldering down a BGA is a very reliable way to make those many connections.

On devices like smartphones & tablets RAM would hardly ever be upgraded even if possible. On laptops most users don't bother. On Raspberry Pi style SBCs it's not doable.

Desktops, workstations & servers are the exception here.

Basically the high-speed parts of a system need to be as close together as physically possible. Especially if low power consumption is important.

Want easy upgrades? Then compute module + carrier board setups might be the way to go. Keep your I/O connectors / display / SSD etc, swap out the CPU/GPU/RAM part.