To be factually clear—Omens launched like September of 2004, WoW launched like the last week of November 2004. Gates was not the current expansion when WoW launched.
I'm just pushing back against a common narrative that WoW made MMOs "carebear", often again, something stated by early EQ players with little modern MMO experience. The things most people identify as being "carebear" in WoW, were already implemented in EQ by the time WoW launched--instanced raiding, less severe death penalty, easier leveling etc. If you ever leveled an alt up to max level (I remember half power leveling / half twinking a Mage up during GoD era because I was in college and had quit raiding), it was like literally ten times easier and faster than going 1-60 was in the "old" EQ days.
GoD also was not mechanically difficult. Like if you actually have done that content in recent memory the vast majority of the bosses have one or two, very simple mechanics. GOD was procedurally difficult for two reasons--reason one is mob damage tables that clearly were made for level 70 raid geared tanks. Gates was originally intended to launch as a new level increase, level 70 expansion. Then they moved something like half the team working on it to SWG, and the development got bogged down and they weren't going to release it in time. So they pared the content down and released like half of what was intended, as a level 65 expansion, but inexplicably didn't retune a lot of the content. There's actually an interview with someone, maybe Holly? That goes into details about the various ills around the development/launch of Gates. The second reason Gates was hard is due to something I already mentioned--buggy or broken encounter design. For example Uqua which was considered a nightmare in its original iteration, had bugs where mobs could attack you through the zone geometry and you couldn't hit them back, and whenever you die in Uqua you spawn a ghost add (that hits hard), those adds pile up and you wipe.
That's not hard in the way that say, a mechanically complex fight is hard, that's hard in the way that "hey I made a really bad game you shouldn't play, but if you do play it, it's broken and doesn't work well" is hard.