Lag ever since the engine update 2-3 leagues ago

I'm not here looking for a fix. I've given up on that at this point.

I would like to know what the engine update did and potentially why so many of us are lagging. I have my suspicions, but would rather ask in the hopes that I'll get a somewhat-accurate response. Does anyone know what the engine update WAS and/or did exactly?...

Thanks in advance.