Off the top of my head:

- No real way to know who is in a cabal or who the leader is, much less anything about the cabal dogma. Good luck getting inducted into a cabal as a newbie. (Usually, a new player's first long-lived-ish caballed character ends up being an enormous leap forward for their game knowledge.)

- Most people don't know what powers cabals even have, much less what they do and how to counter them.

- Knowledge of cabal locations not widespread, and cabals tended to move locations whenever that changed. (Good luck getting your item back from Shadow when you have no idea where it even is.)

- The best players had a sense of how to gear; most players didn't and geared literally everything for pure damroll.

- The best players know tricks to get gear from some really difficult high-end mobs that you weren't realistically going to beat honestly unless you rounded up a dozen people.

- Charm person was still a thing, and one of the consequences of that was that top tier mage/a-p/ninja players knew what and how to charm to stomp you into the dirt.

- Top tier players understood that skill percentages mattered (in many ways, more than today, prereq-based skills/spells excepted) and how to bot them up; most players had no idea they were even all that relevant.

- Mud-wide summon into deathtraps (and a lot higher percentage of characters with summon to go with it) radically increased the advantage of aggressive players.

- One-shot and near-one-shot kill abilities are much, much more common/unrestricted, again increasing the advantage of aggressive players who already have good gear.

- XP being much harder to get + 15k unlimited-stacking XP holes per death = lots of players literally could not hit 50 at all despite constantly trying to level. Imagine playing a character for 200-300 hours and you're like level 20, and you've spent almost all that time trying to get XP.

That's just off the top of my head.