I dislike it, its a RPG and in an RPG you should be given choices.
Realistically speaking, the vast majority of RPGs aren't "free roam" style, have definitive endings, and Just End?. It's only because gamesas games are always free-roam style that people even have this expectation of Fallout3/NV. If it had been from any other company, people would have seen that it ends and been completely ok with it, since they wouldn't have had any different expectations.
after the main quest you can enjoy four guild factions from start to finish, the arena and all of the other numerous side quests, dungeon dive, continue to explore the world, dabble with alchemy...of course all this stuff could be done even before you start the main quest or during the main quest but the point is ALL of this awesome stuff could be done afterwards with no hint of the game ending after the main quest...but your right after the main quest there's nothing to do except mindless killing...
I think his point was that none of those things (play with alchemy, do the arena, do the guilds, etc) is any different before or after the Main Quest ends. Doing them after you close the Oblivion Gates doesn't make them give a different result, or have different quests, etc.