I played a low-level wizard in 2E. My two war dogs were more dangerous than I was.I'm also not overly fond of reducing a creature to what its good for in combat - stat blocks do enough of that already as is (for example, have you ever considered purchasing a guard dog to protect your wizard character because it sounded like a good, fluffy idea vs. dismissing it because of their "bad stats"?)
Ah yes, a classic problem of the DnD community: baulking at a tool that will help you build and run your games easier because you think it’s telling you how you should play.
As promised, here are some examples of existing 5E monster abilities I've identified as helping to act in combat roles. I'd already been looking at these so I could have abilities to bolt onto existing statblocks as needed to quickly customize monsters.
Controller
- Grave Bolt. Ranged Spell Attack. Necrotic damage. If the target is Large or smaller, it must succeed on a Strength saving throw or become restrained as shadowy tendrils wrap around it for 1 minute. A restrained target can use its action to repeat the saving throw, ending the effect on itself on a success.
- Whispers of Compulsion. The creature chooses up to three enemies it can see within 60 feet of it. Each target must succeed on a Wisdom saving throw, or it takes psychic damage and must use its reaction to make a melee weapon attack against one creature of the creature's choice that it can see.
Leader
- Call to Attack. Up to three allies of the creature within 120 feet that can hear it can use their reaction to make a weapon attack.
- Command Ally. The lieutenant targets one ally it can see within 30 feet of itself. If the target can see or hear the lieutenant, the target can make one melee attack using its reaction, if available, and has advantage on the attack roll.
Soldier
- Piercing Claw. Melee Weapon Attack. Reach 15 ft., one target. Piercing damage plus necrotic damage. If the target is a creature, the boneclaw can pull the target up to 10 feet toward itself, and the target is grappled. The boneclaw has two claws. While a claw grapples a target, the claw can attack only that target.
- Furious Defense. After an ally the creature can see is dealt damage by a foe within melee weapon attack reach of it, the creature makes a melee weapon attack against that foe as a reaction.