There is a general approach: use your strengths and ignore your weaknesses. The Academy army will never outshoot Mages, Stronghold, Knight, or Necropolis. So don't even try. Academy will never truly become a shooting faction, but you can suffer greatly in melee and tactics. Why are shooters strong? Because they deal high damage without retaliation, but that doesn't apply to Assassins or Witches, and it's difficult to protect them. If you commit Minotaurs and Hydras to that task, you'll have no one left to fight. Little benefit, plenty of harm. Academy is a hero + melee units with high attack.
The dislike for playing without shooters is a leftover from the times when each of us was just starting to play Heroes; it was easier with shooters. For instance, Death in the fourth game did perfectly fine without any shooters throughout the entire game, and on many maps it was very hard to do anything to them; in the third game, Liches weren't decisive (we don't count the Cloak of the Undead King), etc. Playing without shooters is possible, sometimes even necessary.