It's not just a wall that spits out demons at you. It's a giant ass demon that attacks you in multiple ways. All the while, regular enemies spawn in to hurt you and farm resources. Certain helpful pickups respawn as well which helps a lot when a tough demon is spawned in. Thankfully, no Marauders or Arch Viles spawn in the battle.
The stupid part, IMHO, is that when you have nearly beaten it and just need to jump through a portal to finish it off, it ends up being the exact same battle again! I think the Icon might have a few more attacks the second time around but I'm not really sure.
I much prefer the Spider Mastermind approach from 2016. That one was a bit too easy though as it literally threw you full health twice. So if you had 200hp available, you were in great shape. One time I fought it and there was a glitch where it did not give you health, and it was super difficult. I ended up dying. I'd love to try that again though as I'm sure I could beat her without the freebie health, I'd just have to rethink strategy.