In "Magma Diver," during the first scene inside NERV, we hear over the PA system:

Please expedite transfer of Mt. Asama observational data from Balthasar to Melchior as soon as possible.

Aren't the Magi supposed to be networked together? Why, in 2015, would someone need to give this order over the PA instead of email, instant messenger, or simply opening up a prompt and issuing a command?

Well, I think because this was a lot of data stored on several hard drives or magnetic tapes. When I was doing my master's degree in computer science, I recall talking to one researcher who shuffled huge amounts of data around his lab. He said that by the time one you'd finished waiting for one machine to copy its data to another, you might as well just have popped out the hard drive and walked it over and plugged it into the other machine.

It must have been a massive (and urgently needed!) amount of data that NERV collected from Mt. Asama that lazily waiting for the network wasn't good enough. Ritsuko doesn't seem to be involved in this effort, as we see her talking to Misato immediately afterwards about how the pilots are going to miss the school trip to Okinawa. So, the way this order was given, it seems like this is a big but easy job, the kind for multiple junior NERV people.

How much? Well, until we get more info, like a canon answer to the Magi's system specifications, we may never know.

The 2015 of NGE is not our 2015 (they don't even have iPhones). Some of the in-world explanation can be pointed at the economic effects of Second Impact, of course, but for the MAGI, those are clearly some Project E weird tech spin off - the brain-like structure we see when Ritsuko goes delving into the innards of the system, for example.

A current year handwave would be that the transfer delay is not in the moving a terabyte USB stick from one unit to the next; it's in the LLM training times for a different bespoke (literal) neural net computer for it to be able to understand the raw bits and bytes.

Never underestimate the bandwidth of a station wagon full of tapes hurling down the highway./

Data transfer can be fast but slow or slow but fast.

^yeah, that. For massive amounts of data, just moving physical hardware is faster, and ironically often times more secure, which would definitely be a priority for Nerv.