There's no "issue", this is purely SE pretending that the game is booming with players while in fact... it isnt.
https://steamcharts.com/app/39210
We havent been at such a low point since december 2023, where is the so called congestion ? Why is Balmung open for new character creation, while at the same time being congested for world visit and DC travel ? Those are both good questions to ask yourself and question if any of this "congestion" makes any sense at all.
Even the so called "aether is the raiding dc" has simply moved to primal, people will always congregate on the same servers and datacenters, this happens in every single MMO and FFXIV isnt exempt from that.