very different actually, gameplay back then was more sandbox. No instanced missions all bosses and raids were open world. Long quest to obtain the key to Vex Thall which was the big raid zone. key quest included obtaining 10 staff pieces a frame and two orbs one orb from a minor boss and a second orb from Emporer Ssra who could only be damaged from melee by Shisar bane weapons you had to get and to get to Emp Ssra you had to farm key parts in Ssra Temple I think there were like 5 pieces you had to get for it. It also launched the Bazaar and Mounts. The fastest mounts dropped from Emp Ssra and Lord Seru. Lord Seru also had a key quest but fortunately, only one person per group had to have the key. He also could only be damaged by melee with Seru bane weapons which you had to farm.
Now everything is instanced both raids and group content. You do have the merc and partisan quests though in the open world and some group named. Armor is different too back then there was no class-specific armor in Luclin like now which is strange because both Kunark and Velious had class-specific armor. They went back to it for PoP.