Despite its slightly higher damage and ammo-to-reload ratio, this card is outclassed by Monkey Investigator, which costs 3 Gold instead of 4 and has a useful On Play effect; Mine Supervisor, which has the same cost and DPT but also generates Bloontonium; and Sniper Monkey, which has better DPT and burst damage and costs 3 Gold instead of 4. Crossbow Monkey's few benefits over Sniper is that it can be affected by Super Monkey Fan Club, it has better burst buffing potential, and it has more flexible targeting.
Crossbow Monkey does one-shot Red Bloons outside of Dark Castle, unlike Monkey Investigator outside of Game Night.
Crossbow dealing 80 damage allows it to pop Blooming Bloon if it has no Health buffs.
On a deck that relies on Fan Club synergy to defend, Crossbow is still a questionable choice, as its buffing power isn't higher than most other dart monkeys. Bringing it if combined in a deck with a mid-game win condition to defend for a while before the final kill can be a decent budget strategy.