I love LOTR 3. However, I haven't played LOTR 1 nor 2, so I can't really see how bad the game is from your angle. But I think I do understand what you mean when you say that this RTS-dazzling-too-fast-speed-junkey-comatose game is just such a disappointment. I'll give a shot at explaining what I think is so utterly brilliant about this game and also try to describe how to play LOTR 3 in order to get a good experience instead of the feeling that you're constantly getting rushed by the AI.
For starters, you obviously can't think in the same way as you can in a turn-based game such as its predecessors. But there is an option to play in "slow" mode (options -> gameplay -> game speed), actually making the game a lot easier. As it is an RTS, you can never predict the actions of the AI in advance, which is why you need to pay constant attention to your lands and watch out for any enemy advances in your territories. You should also always leave some armies behind so that you may fend off the AI if he happens to take your castle. Getting rushed is a part of the newbie experience of the game. At first you will hate LOTR3 because it's just so damn hard, but after some days, you will learn how to maneuver in order to delay the AI and turn his disadvantages into your advantages. After a while, you'll realize that the AI is actually very mindless and not very strategic at all.
This is all part of my own experience: the first times I played LOTR3, all the campaigns seemed virtually impossible to complete. I remember how happy I was when I could take control of Ireland. After I got the hang of it, the game was much more fun to play. :)
The brilliance of this game comes much later in the gameplay, and that is the complexity of the vassals. Some vassals are just useless and some are OP. Attracting the right vassals will win you the game. It's not micromanagement, but it's pure strategy, and it is more elegant than you may think. For instance, say you want a high Christianity to get you the sweet Knight Hospitaliers and Templars. This requires that you maintain a lot of churches in your parcels, leaving you quite vulnerable in the early game. So if you want the better knights in the early game, you will need to play passively and war as little as you can. But then the AI keeps using the Corrupt Cardinal against you, reducing your Christianity to nothing. To ward against the Corrupt Cardinal, you'll have to attract a Saintly cleric (The Prophet/The Martyr). In order to attract this cleric, you'll need to maintain a level 4 Cathedral in your lands for a given time. But your Estate parcel is only level 2! In order for it to develop, you should use a Cleric with a Seneschal ability (The Seneschal ability makes the parcel develop faster).
Etc Etc Etc. There are tonnes of abilities that will grant you advantages in military, politics and economics. Some serfs, burghers and clerics can add companies to the knights in the same region. If you manage to attract enough of these, a knight can be a one-man army. And not to mention the orders, that give you bonuses within certain areas. Command enough Teutonic Knights and you'll have Grandmaster Teutonic Knights in your vassal pool.
All in all, there is so much more in this game than what meets the eye. Think of it as a giant game of cards. Play your cards right to get better cards and use them against your opponent. You just have to find out which ones that you need to play - it all comes with experience. It's really fun. Think twice before you put it in the bin, please.
