Many of your points are valid Stone Mill. I don't suggest that KOTH is the only way to play. And do not suggest a player good at KOTH would be good at all types of SEIV games. That variety is one fo the beauties of SEIV.
Even if every player has the 20/20/berzerker traits you suggest, that still leaves 13 characteristics to tweak and all the advanced traits to choose from in an effort to gain an advantage over your opponent. There is still lots of room for variety in empire setup. Koth is a min/maxers dream.
And then there is the luck of the starting positions to account for. And in-game execution of strategy.
I think a good indication of the popularity of the format is the players that keep coming back for more even though they keep getting spanked.
Finding the formula for victory is the challange. Your suggestions are just one ingredient. An important one, but still just a part of the overall picture.
Personally though I would love the challange of a default or same empire setup. I think more than a few people would give it a try if it were suggested. Kind of like a stock car race. Then you'd really know it was all the skill of the driver.
Geoschmo