For the first couple of years, despite the bugs, AoC had some of the best PvP and most fun in any MMO, so long as you didn’t mind dying. 
Zergs in kesh, constant premades, even lagfest sieges and the gem days had some novelty to them.
Personally, 1.04 and 1.05/1.06 hold a special place in my heart as the best time for this game. The AA grind didn’t exist, gear wasn’t nearly as important as it is now ( although casters were seriously bonkers OP in 1.05/1.06 due to the complete and utter lack of any protection gear, period ), and the population was still large, albeit thinned down from release. Cool mechanics like combo canceling (not molding) were present, allowing the game to have an incredibly high skill ceiling. Combined with stamina management, melee was an incredibly difficult role to play with infinite room to improve. In my mind, the ideal AOC PvP environment would be 1.06 where everyone starts with pvp5 gear + weapons.
Unfortunately, when khitai + pvp10 came out, pvp pretty much evaporated as the original grind to pvp10 was so long and horrible, where shrines of bori was the only way to gain conquest trophies for the DRASTICALLY overpowered pvp10 gear. Funcom hadn’t yet buffed PvP T1 yet, and the difference back then between t1 and t3 was HUGE. I don’t have any old screenshots, but the old pvpt1 boots, gloves, belt, wrists, shoulders, rings, cloak, and necklace were all “blue” quality gear, and the pvpt3 gear was significantly better + levied a huge advantage if you afk farmed bori with your zerg guild.
Many people here may remember khitai + pvp10 fondly because they were the first to attain the gear and it levied a huge advantage, but that crap literally alienated any casual pvp focused player or anybody who did not want to grind for hours every day in order to reach a competitive level. While AA’s allowed for some cool customization, broken AA like the original Taking the Shot, Prime Initiative, At the Gates, added another level of grinding for players, many of which did not play AoC to grind.
( I left VoM off that list because when first implemented, most players had ~5% crit. A DT with 5% crit and VoM was nearly as useless as a DT without VoM. )
Fast forward to today and now you have tanks running around in frenzy with 30% mitigations and over 16000 health with abilities that heal them for 200/second every minute.
It baffles me that the PvE in this game is the most popular activity. While it is fun, most of the encounters aren’t very complex or involved, but usually boil down to a single mechanic + tank and spank.