What exactly did he say that was so wrong?
i was referring to his (or her) disdain for the trinity...or more generally the preference for games where either: one player can play any role at a given time (which is what i believe he is getting at) or a game that either doesn't have specific roles, or does but specific roles are not needed to consume content.
I've played games that required the trinity and games that have not and w/out fail the games that have required the trinity have been much more enjoyable. The games that have not have almost universally bombed (both with me and in general), even though in theory you would think they would be more fun. That's part of the problem imo...too much of game design now revolves around game theory and accessibility and "fun all the time with no hurt feelings"...vs just plain making a game that draws you into it's world. That to me more than anything else is what is causing the overwhelming glut of crap we have seen over the last 5-10 years.
Why is the trinity more fun to me? Hard to put easy/specific reasons down but i think it comes down a combination of the following:
1) PCs having defined roles makes for a more interesting world. W/out defined roles, everyone ends up virtually the same and the only thing that differentiates you is skill level. That makes for a really boring game world for me (realize a lot of this is personal pref). EQ was a wonderful "world" in large part to me because you had many different classes and so many people became identifiable in part because of the class they chose. You had great tanks and great clerics and great rogues and great monks and great rangers etc. etc., but you didn't have any single person that was a great tank/cleric/rogue/monk/ranger...because if you had that then eventually everyone would be a great tank/cleric/rogue/monk/ranger at which point everybody would be the same.
Or to summarize: W/out defined roles everyone basically end up the same. And everyone being the same = bad, bland, boring as hell game world.
2) Given 1 above where different roles are required and everyone to a certain extent is locked into a certain role, you then need to require certain roles to be a necessary part of a good group to play the game. Otherwise you end up with roles that nobody needs which makes those players essentially worthless...and this i think everyone can universally agree would not be a good thing. So- from this requirement that all roles have a necessary place in the game comes the holy trinity. Every class should have a place somewhere within the holy trinity so that they are needed (with an exeption) and the "necessity of interdependency" becomes an important aspect of the game.
The exception to #2 might be classes that are more solo-oriented (like necros, or maybe even bards to an extent in EQ). I think giving people this option is very important because some people are just more solo-oriented, but then realize you won't be able to do some high-level dungeon or take down some big boss alone. But even this adds more depth to the game world.
So, at the end of the day i think you have 3 main choices around character design:
1) holy trinity with people locked into certain classes
2) holy trinity but everyone can play any role in the trinity at any given time
3) no holy trinity required (and generally no specific classes...think something similar to Skyrim)
I see 2 and 3 as being not a legitimate way to go for the reasons i stated above, leaving option 1. Options 2 and 3 generally lead to everyone being the same at some level which imo is a very bad thing for MMORPGs.