I would like to give some precisions about the way attrition is working to explain that is REALLY a FUN aspect of the game and not 'an historical cheat' made for game balance.
First of all, attrition is the ONLY factors that can explained that some HUGE armies have been destroyed by smaller one. I will give some exemples about EU period: the invicible armada has been defeated by english navy BUT has been DESTROYED by attrition because they have nee to make turn of UK during storm season. Napoleon (just a bit after EU) has nearly lost 500K due to attrition in Russia in 1812 which has directly made him lost all his power.
United States have become independant because England has been cut from his supply sources at the end of the war.
What does it means in FUN for EU.
It simply means that this is NOT a game where 'I have more guns than you, so I am the winner' like Imperialism can be. Of course it could be fun to play sometimes wich such games but I never play on it as much as I haved play EU during beta test. In term of game, attrition will signify that you will have to think twice before decide wich strategy you will use.
I can said to you: attrition is probably one of your best weapons as a human player, for 2 reasons.
The first one is that it will probably damage much more your opponent than your army, especially if you use a scorched earth tactic. I promise you, it is REALLY possible to play such a tactic with EU, that was impossible in Imperialism. I think that when you will have played one or two times Russia in EU, you will really appreciate such a thing.
The second one is that attrition cost you nothing when it destroyed some parts of the ennemy. As money is extremely important when making war, everything that cost nothing to you is good to take.
The other thing that we probably have not good explain, is that attrition depend greatly from WHERE you are and WHEN.
For exemple, Paris can contains a massive army even during winter. On the other side, some territories around Hudson bay, are simply a hell for army (If some canadians are present here, they will probably confirm that North Canada is not a really pleasant place to live in during winter without a good fuel heater

)
What does that means in term of FUN for EU:
It said that most of battles will occurs on plains during summer. But nothing prevent you, if you have a good maneuvring leader, to make a strategical surprise by walking through a less 'adequate' province. This means that you will arrive on the back of your ennemy with only some loses due to attrition. Here you will be able to looted and pillage most of his provinces greatly reducing him money.
The last point is that attrition is the most important weapons for some countries: England, Russia, Turkey, Sweden.
For this countries, attrition will signify that they ennemies will loose time and men just to arrive to the contact of their own troops.
Can you really imagine that England would have remain an independant country during this period, if the Channel was not here, to stop and slow french army?
In game play, that will signify that the English player will be able to see French concentrating force and loose time and men to cross. This delay is sufficient for England to send troops to the menace.
About tech level at start of scenario, I have seen people claims that it was a scandal that a country has one point more than another. Everybody should be aware that speculate of the effect of one point difference in tech, is like pretending that 50 cents is the sum that will made a 100$ note worth nothing.
I hope that I have been to explained in which sense attrition is really a fun aspect of war in EU, and that give really more strategical and tactical wealth to EU.