Magnetic tapes are still one of the best ways to store large quantities of data over a very long period of time, and they typically don’t really need very fast I/O considering their use case as long term archival that the stored data may or may never be read again.
RAM and local device storage are very much different story, considering the performance implications; it’s pointless to have a lightning fast processors if RAM and storage bus speeds can’t keep up. That said, flash memory doesn’t last forever, and there is a strong case to be made about having swappable components that don’t brick the entire machine when they fail. Replaceable parts ensures a device can live longer, leading to less ewaste and less money needlessly spent.