AOE2 is wonky, but that's what makes it good.
Villagers collide with each other, forcing you to find new tree-lines (compared to Starcraft/Starcraft2 SCVs/workers which "stack" on each other for maximum mineral collecting at all times).
Units in AOE2 move terribly, minimizing what you can do with micro (sure, micro is still possible, but this ain't no "magic box Psi Storm", nor a 11-muta harass here). AOE2 "micro" is largely delegated to patrol-shennanigans and "zvzvzvz" (staggered formation / flank-formation) for dodging magonel shots.
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SC2 had units deathball too easily with perfect flocking behavior. The 90s-style crappy flocking behavior / collisions (aka: idiotic Dragoons from SC:Brood War or AOE2 pathing issues) somehow balances the game for the better.
Once units "deathball" too easily, you end up with well... deathball-style combat. By making units get less-efficient the bigger the group (ie: Dragoons going the wrong direction or getting stuck in paths, or AOE2 units running around not understanding how to attack the damn enemy cause the group is too big), it forces the players into controling smaller groups and more strategically using them.
Which seems like more fun? Its annoying because the "units don't do what you want them to do" (and SC2 units really "do what you want them to do"). But... somehow its less balanced with the SC2 approach.
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The key to a good strategy game is to accept and recognize the duality of Lanchester's Linear Law (ie: Risk rules), and Lanchester's Quadratic Law (ie: Axis and Allies).
If you overly focus on the Quadratic law, you end up with death-balls.
If you overly focus on the linear law, it feels like additional units don't support each other and the game feels very flat (ie: Risk-like).
But if you have a rich continuum between the two laws, you end up with great gameplay (Starcraft: Brood War, AOE2, and Hearts of Iron 3).
Let units get quadratically stronger as they flock together... but only to a point. (IE; the size of the front in Hearts of Iron 3. Or until the "Magic Box size" in Starcraft:Brood War). Once the units grow beyond that, they need to be hampered and grow more linearly, encouraging a more diverse set of combat situations.