The Ranger Beast Master subclass gets an animal companion under the ranger companion ability, which for free can move about the battle field, or using the Ranger’s action can make an attack. Being a cr 1/4 creature, that attack is generally worse than the attack the ranger has by the time he gets the companion.
If the ranger was multiclassed a rogue, I could see the use of the companion moving about to be adjacent to enemies, but I’m not seeing what synergizes well without multiclassing.
Am I missing something, or should I tell my friend that his assessment is correct, and he should only choose the beast master if he wishes the fun of his animal companion but that the creature itself will not actually synergize very well with his class abilities?
I prefer a rules as written answer.