My dudes... it's the freaking hardware.
The idea that "it's the code" is a red herring sold to you by past and present devs so they can deflect blame in what is effectively a corporate main office issue and correct answer; which is to buy better hardware.
Think about it, compare some of the modern multi-player games vs. this 20 year old "pong-like" MMO, there's zero comparison. Case in point the massive EVE online battle that took place involving 5,000 players and 100 capital ships costing almost half a million dollars (yes U.S. dollars) in damages to in-game items.
And if you know EVE you know one capital ship does more calculations than all of Orien server. It was crazy:
So, it was never the code; the bottleneck was ancient hardware from a bygone era of MMO games.
WoW classic is currently entirely 64-bit, they can accomodate thousands of concurrent players and there is seemingly zero lag anywhere.
Anyway, Tolero said that things are going so well that there is a possibility we'll be transferring off these 32-bit rust buckets by
end-of-year!
Tolero... please hurry! I can't hold off the disenchanted players for much longer!