See the problem is Vortex doesn't exist in a vacuum. It exists among all the other unique and non intuitive aspects of the server. When a new player joins, they need to contend with personas, chat channels, emoting, and a million other things scream for their attention. One of the top new player complaints when I was on the team was just how different and restricted LoTC felt compared to the vanilla experience. Some people call that a pro but if you're going to make a roleplay server on Minecraft, you should at least lean into the Minecraft's strengths. The server should be intuitive for someone who's already familiar with vanilla Minecraft.
From what I could tell, Vortex is required if you want to craft any of the new PvP items. It also looks like the world team wants to use Vortex to simulate some sort of economy, I really wouldn't call it "optional".
The idea that it's somehow the player's fault developers made a system that requires a written guide to use is bonkers......The goal should be to make the server more welcoming and easier to get into. Also, I'm not sure where you got the idea that the application process is in any way rigorous. The major complaint for apps over the last 2 years has been it's too easy lol.
And this is all without actually addressing the fact that the GUI looks pretty awful. Do we really need to be using glass panes? It's not that much more work to introduce a server resource pack and use blank textures. And if you don't want to introduce a customer resource pack for whatever reason, you could at least use heads for the various icons......