This is exactly why AQ is not a good feature for AOE2. The combat system is just not interesting enough to put so much focus on it. Just take a look at all the military units there are. Nearly all of them basically do 2 things all the time: Move, Attack. Thats it. The only unit which is somewhat special is the monk, having the ability to heal, collecting relics and having a large cooldown on its attack (convert is basically an attack). Maybe you can argue for things like mangonels with their splash and attack ground. There are no special abilities you can reasearch for your units to use, there are no units that can move around the map in an interesting way like climbing cliffs. It is mostly just plain old selecting your units and smack in some other faces.
To me this just sounds like a boring game. Using hit & run with your archers for 30 minutes every game sounds fun for the first few games, not for the next 1000. The reason a combat system like that is working for so long is because it is simply not the main focus of the game. The biggest challenge is spending all your resources in a meaningful way. Take away this challenge, which auto spending resources does help incredible a lot with, and the main focus of the game will shift more towards the military side and as I already mentioned: It just sounds boring.