Back then we'd have like 50+ players in every zone. Many peeps were on dial up modem lines - look up Wikipedia if you have no idea what this is - but basically it was slow ass and unreliable internet.

Add to this computers that were maybe 1/20 as powerful (guessing) as a today's $200 android phone, and splitting big dense zones into smaller ones starts to make sense.

Right - the limitation in 2016 is purely software, e.g. the shitty Titanium client. It would need a complete overhaul in order to rewrite its caching system and then have the client and server actually know what to do when you hit a zone line and all of the data is immediately available. That would be amazing though - just a brief milliseconds-long pause for the server to relay information before you're in the next zone. Screw EQ in the Unity engine, this is what those EQEmu nerds should be working on.

I have dual SSD and it loads fast, but it could always be instantaneous